T-348 - 072012 Air Condiction Mci D4500

T-348 Manual
OPERATION AND SERVICE

for
68AC353-102
MICROMAX
T-348
REV. 07/2012
© 2012 Mobile Climate Control

TABLE OF CONTENTS
SAFETY SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Safety-1
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.2 CONFIGURATION IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3 OPTION DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.1 Condenser Cover (Skins) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.2 Condenser Electrical Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.3 Condenser Fan Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.4 Condenser Refrigeration Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.5 Evaporator Skins Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.6 Evaporator Blower Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.7 Evaporator Connection Kit S/D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.8 Evaporator Connection Kit - Indash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.9 Evaporator Connection Kit (Heating) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3.10 Air Exchange Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3.11 Controller Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.4 GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.4.1 Compressor Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.4.2 Discharge Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.4.3 Rooftop Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.4.4 Condensing Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1.4.5 Evaporator Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
1.4.6 Fresh Air System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
1.4.7 System Operating Controls And Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
1.5 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS . . . . . . . . . . . . . . . . . 1-8
1.6 ELECTRICAL SPECIFICATIONS - MOTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
1.7 ELECTRICAL SPECIFICATIONS - SENSORS AND TRANSDUCERS . . . . . . . . . . . . 1-9
1.8 SAFETY DEVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
1.9 AIR FLOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
1.10 AIR CONDITIONING REFRIGERATION CYCLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
1.11 HEATING CYCLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
1.12 CONTROL PANEL WITH GR60 RELAY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
1.13 CONTROL PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15
1.14 LOGIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
1.15 RELAY BOARD - GR60, 24VDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17
1.15 RELAY BOARD - GR60, 24VDC (Continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
1.16 RELAY BOARD, 24VDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
1.17 LOGIC BOARD, DATA COMMUNICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
1.18 CONTROL PANEL (Diagnostic Module) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1 STARTING, STOPPING AND OPERATING INSTRUCTIONS . . . . . . . . . . . . . . . . . . 2-1
© 2012 Mobile Climate Control 1 T-348 Rev. 07/2012

TABLE OF CONTENTS - Continued
2.1.1 Power to Logic Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1.2 Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1.3 Self-Test and Diagnostics (Check for Errors and/or Alarms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1.4 Stopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.2 PRE-TRIP INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.3 MODES OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.3.1 Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.2 Cooling Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.3 Heating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.4 Boost Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.5 Vent Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.6 Compressor Unloader Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.7 Evaporator Fan Speed Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3.8 Condenser Fan Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3.9 Compressor Clutch Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3.10 Liquid Line Solenoid Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3.11 Alarm Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3.12 Hour Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.4 MICROPROCESSOR DIAGNOSTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.4.1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.4.2 Diagnostic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.4.3 System Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.4.4 Test Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1 SELF DIAGNOSTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2 SYSTEM ALARMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2.1 Alarm Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2.2 Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2.3 Alarm Queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2.4 Alarm Clear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2.5 Exit Alarm Queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.3 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.3.1 Troubleshooting No CAN Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.3.2 System Will Not Cool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3.3 System Runs But Has Insufficient Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3.4 Abnormal Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3.5 Abnormal Noise Or Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3.6 Control System Malfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.7 No Evaporator Air Flow Or Restricted Air Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.8 Expansion Valve Malfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.9 Heating Malfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1 MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 OPENING TOP COVER (EVAPORATOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.3 REMOVING TOP COVER (CONDENSER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.4 SUCTION AND DISCHARGE SERVICE VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.4.1 Installing R-134a Manifold Guage Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.5 PUMPING THE SYSTEM DOWN OR REMOVING THE REFRIGERANT CHARGE 4-4
4.5.1 System Pump Down For Low Side Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
4.5.2 Refrigerant Removal From An Inoperative Compressor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
4.5.3 Pump Down An Operable Compressor For Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
4.5.4. Removing Entire System Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
4.6 REFRIGERANT LEAK CHECK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
4.7 EVACUATION AND DEHYDRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.7.2 Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.7.3 Procedure for Evacuation and Dehydrating System (One Time Evacuation) . . . . . . . . . . . . . . . . . . . . . . 4-8
4.7.4 Procedure for Evacuation and Dehydrating System (Triple Evacuation) . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.8 ADDING REFRIGERANT TO SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.8.1 Checking Refrigerant Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.8.2 Adding Full Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
4.8.3 Adding Partial Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
4.9 CHECKING FOR NONCONDENSIBLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
4.10 CHECKING AND REPLACING HIGH OR LOW PRESSURE SWITCH . . . . . . . . . . . 4-9
4.11 FILTER-DRIER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
4.11.1 To Check Filter-Drier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
4.11.2 To Replace Filter-Drier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
4.12 SERVICING THE LIQUID LINE SOLENOID VALVE . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4.12.1 Coil Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4.12.2 Internal Part Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4.12.3 Replace Entire Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4.13 THERMOSTATIC EXPANSION VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
4.13.1 Valve Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
4.13.2 Superheat Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
4.14 REPLACING EVAPORATOR RETURN AIR FILTERS . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
4.15 COMPRESSOR MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
4.15.1 Removing the Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
4.15.2 Transferring Compressor Clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
4.15.2 Transferring Compressor Clutch (Continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
4.15.3 Shim-less Compressor Clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
4.15.4 Compressor Oil Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
4.15.5 Checking Unloader Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
4.16 TEMPERATURE SENSOR CHECKOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
4.17 PRESSURE TRANSDUCER CHECKOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

4.18 REPLACING SENSORS AND TRANSDUCERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
4.19 LOGIC BOARD REPLACEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
ELECTRICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5-1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
LIST OF FIGURES
Figure 1-1 System Component Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Figure 1-2 Rooftop Unit Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
Figure 1-3 Condensing Section Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Figure 1-4 Evaporator Section Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
Figure 1-5 System Air Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
Figure 1-6 Refrigerant Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
Figure 1-7 Heat Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13
Figure 1-8 Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Figure 1-9 Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-15
Figure 1-10 Logic Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-16
Figure 1-11. Relay Board - GR60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17
Figure 1-11. Relay Board - GR60 (Continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
Figure 1-12. Relay Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19
Figure 1-13 Logic Board, Data Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-20
Figure 1-14 Micromate Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21
Figure 2-1 Capacity Control Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Figure 4-1 Opening Top Cover (Evaporator) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Figure 4-2 Condenser Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Figure 4-3 Suction or Discharge Service Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Figure 4-4 Manifold Gauge Set (R-134a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Figure 4-5 Compressor Service Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Figure 4-6 Service Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Figure 4-7 Checking High Pressure Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Figure 4-8 Filter-Drier Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Figure 4-9 Liquid Line Solenoid Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
Figure 4-10 Thermostatic Expansion Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Figure 4-11 Thermostatic Expansion Valve Bulb and Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Figure 4-12 Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Figure 4-13 Removing Bypass Piston Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Figure 4-14 Compressor Clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Figure 4-15 Transducer Terminal Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Figure 5-1. Wiring Schematic - Legend (PM Motors) - 68AC353-102, 102-4, 102-5 . . . . . . . . . . . . . 5-2
Figure 5-2. Wiring Schematic - Control Circuit (PM Motors) - 68AC353-102, 102-4, 102-5 . . . . . . . 5-3

Figure 5-3. Wiring Schematic - Power Circuit (PM Motors) - 68AC353-102, 102-4, 102-5 . . . . . . . . 5-4
Figure 5-4. Wiring Schematic - Legend (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6 . 5-5
Figure 5-5. Wiring Schematic - Control Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6 .
.............................................................................. 5-6
Figure 5-6. Wiring Schematic - Power Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6 . .
.............................................................................. 5-7
Figure 5-7. Wiring Schematic - Condenser Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6
.............................................................................. 5-8
Figure 5-8. Wiring Schematic - Evaporator Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6
.............................................................................. 5-9
Figure 5-9. Wiring Schematic - Legend (Brushless Motors) - 68AC353-102-2 & 102-7 . . . . . . . . . . . 5-10
Figure 5-10. Wiring Schematic - Control Circuit (Brushless Motors) - 68AC353-102-2 & 102-7 . . . . 5-11
Figure 5-11. Wiring Schematic - Control Board Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7
.............................................................................. 5-12
Figure 5-12. Wiring Schematic - Condenser Motor Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7
.............................................................................. 5-13
Figure 5-13. Wiring Schematic - Evaporator Motor Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7
.............................................................................. 5-14
LIST OF TABLES
Table 1-1 Option Legend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Table 1-2 Option Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Table 1-3 Additional Support Manuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Table 2-1. Unloader UV1 Relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Table 2-2. Unloader UV2 Relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Table 2-3 Evaporator Fan Speed Relay Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Table 2-4. Controller Test List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
Table 2-5. Parameter Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Table 3-1 Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Table 3-2 Alarm Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Table 3-3. General System Troubleshooting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Table 4-1 Temperature Sensor Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Table 4-2 Pressure Transducer Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Table 4-3 Logic Board Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
Table 4-4 R-134a Temperature - Pressure Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20

SAFETY SUMMARY
GENERAL SAFETY NOTICES
The following general safety notices supplement the specific warnings and cautions appearing elsewhere in this
manual. They are recommended precautions that must be understood and applied during operation and
maintenance of the equipment covered herein. A listing of the specific warnings and cautions appearing
elsewhere in the manual follows the general safety notices.
FIRST AID
An injury, no matter how slight, should never go unattended. Always obtain first aid or medical attention
immediately.
OPERATING PRECAUTIONS
Always wear safety glasses.
Keep hands, clothing and tools clear of the evaporator and condenser fans.
No work should be performed on the unit until all start-stop switches are placed in the OFF position, and power
supply is disconnected.
Always work in pairs. Never work on the equipment alone.
In case of severe vibration or unusual noise, stop the unit and investigate.
MAINTENANCE PRECAUTIONS
Beware of unannounced starting of the evaporator and condenser fans. Do not open the unit cover before
turning power off.
Be sure power is turned off before working on motors, controllers, solenoid valves and electrical controls. Tag
circuit breaker and power supply to prevent accidental energizing of circuit.
Do not bypass any electrical safety devices, e.g. bridging an overload, or using any sort of jumper wires.
Problems with the system should be diagnosed, and any necessary repairs performed by qualified service
personnel.
When performing any arc welding on the unit, disconnect all wire harness connectors from the modules in the
control box. Do not remove wire harness from the modules unless you are grounded to the unit frame with a
static-safe wrist strap.
In case of electrical fire, open circuit switch and extinguish with CO2 (never use water).
UNIT HAZARD LABEL IDENTIFICATION
To help identify the hazard labels on the unit and explain the level of awareness each one carries, explanations
with appropriate consequences are provided below:
DANGER
Indicates an immediate hazard which WILL result in severe personal injury or death.
WARNING
Indicates hazards or unsafe conditions which COULD result in severe personal injury or death.
CAUTION
Indicates potential hazards or unsafe practices which COULD result in minor personal injury, product or
property damage.
© 2012 Mobile Climate Control Safety-1 T-348 Rev. 07/2012

SPECIFIC WARNING AND CAUTION STATEMENTS
The statements listed below are applicable to the refrigeration unit and appear elsewhere in this manual. These recommended
precautions must be understood and applied during operation and maintenance of the equipment covered herein.
SPECIFIC WARNINGS AND CAUTIONS
WARNING
Be sure to observe warnings listed in the safety summary in the front of this manual before
performing maintenance on the hvac system
WARNING
Read the entire procedure before beginning work. Park the coach on a level surface, with park
ing brake applied. Turn main electrical disconnect switch to the off position.
WARNING
Do not use a nitrogen cylinder without a pressure regulator
WARNING
Do not use oxygen in or near a refrigeration system as an explosion may occur.
WARNING
The filter-drier may contain liquid refrigerant. Slowly loosen the ORS hex nuts to avoid refriger
ant contact with exposed skin or eyes.
WARNING
Battery disconnect should be off.
WARNING
Extreme care must be taken to ensure that all the refrigerant has been removed from the com
pressor crankcase or the resultant pressure will forcibly discharge compressor oil.
CAUTION
Do not under any circumstances attempt to service the microprocessor. Should a problem de
velop with the microprocessor, replace it.

CAUTION
To prevent trapping liquid refrigerant in the manifold gauge set be sure set is brought to suc
tion pressure before disconnecting.
CAUTION
Use care when checking/manipulating wires/plugs attached to the Logic Board. Damage to
the board or wiring harness can occur.

SECTION 1
DESCRIPTION
1.1 INTRODUCTION curvature of the bus roof. The assemblies available
are identified as the 10 M radius cover and the 6.5 M
This manual contains Operating Instructions, radius cover.
Service Instructions and Electrical Data for the
Model 68AC353 Air Conditioning and Heating 1.3.2 Condenser Electrical Kit
equipment furnished by Mobile Climate Control as The 68AC353 condenser kits are wired for either 24
shown in Table 1-1 and Table 1-2. Additional Volt permanent magnet motors or 24 Volt brushless
support manuals are referenced in Table 1-3. motors.
The Mobile Climate Control model 68AC series 1.3.3 Condenser Fan Kit
units are of lightweight frame construction, designed
to be installed on the vehicle roof. The 68AC353 condenser kits are available with either
4 or 6 fans, with either permanent magnet or
Model 68AC353 systems consists of a condensing brushless motors.
section, evaporator section and an engine
compartment mounted compressor. To complete 1.3.4 Condenser Refrigeration Kit
the system, the air conditioning and heating The 68AC353 condensers are all fitted with a
equipment interfaces with electrical cabling, condenser coil, a receiver with sight glasses and
refrigerant piping, engine coolant piping (for fusible plug, a charge isolation valve and
heating), duct work and other components interconnecting tubing.
furnished by the bus manufacturer. See Figure 1-1.
1.3.5 Evaporator Skins Kit
Operation of the units is controlled automatically by
a microprocessor based Micromax Controller which The evaporator section may be fitted with one of two
maintains the vehicle's interior temperature at the different cover assemblies dependent upon the
desired set point. curvature of the bus roof. The assemblies available
are identified as the 10 M radius cover and the 6.5 M
1.2 CONFIGURATION IDENTIFICATION radius cover.
Unit identification information is provided on a plate 1.3.6 Evaporator Blower Kit
located inside the condenser and evaporator The 68AC353 evaporator kits are available with
sections. The plate provides the unit model number, either 4 or 6 blowers, with either permanent magnet
the unit serial number and the unit parts or brushless motors.
identification number (PID). The model number
identifies the overall unit configuration while the 1.3.7 Evaporator Connection Kit S/D
PID provides information on specific optional The evaporator units are assembled to allow
equipment and differences in detailed parts. orientation of the connections for different
The following paragraphs provide descriptions of mounting arrangements and may be supplied with
the options provided. A tabular listing of unit model various refrigerant piping layouts for specific
numbers and PID numbers, used to assist the reader applications.
in identifying the equipment supplied is provided in 1.3.8 Evaporator Connection Kit - Indash
Table 1-1 and Table 1-2.
The evaporator units are assembled to allow
1.3 OPTION DESCRIPTION connections for various refrigerant piping layouts for
remote evaporators.
Various options may be factory or field equipped to 1.3.9 Evaporator Connection Kit (Heating)
the base unit. These options are listed in the tables
and described in the following subparagraphs. The evaporator units are assembled to allow
1.3.1 Condenser Cover (Skins) orientation of the connections for different
mounting arrangements and may be supplied with
The condenser section may be fitted with one of two various engine coolant piping layouts for specific
different cover assemblies dependent upon the heating applications.
© 2012 Mobile Climate Control 1--1 T-348 Rev. 07/2012

1.3.10 Air Exchange Kit 1.3.11 Controller Kit
The unit will be fitted with a fresh air exchange The Micromax Controller operates the system
assembly or an air exchange blank off plate. Fresh air through one of two relay boards and may be
exchange assemblies may be of the 25% or 50 % interrogated through the optional CAN +/- Data
opening. Communication Link.

Table 1-1 Option Legend
OPTION DESCRIPTION OPTION DESCRIPTION
Condenser Skins Kit Evaporator Connection Kit S/D
1 Standard Cover (R10M) 1 Left - ORS
2 Cover (R6.5M) 2 Right - ORS
Condenser Electrical Kit Left - ORS With Out Front Box
3 Connection
1 Condenser Electrical Kit
2 Condenser Electrical Kit / Brushless Evaporator Connection Kit - Indash
Condenser Fan Kit 1 Right
1 24 Volt With 4 Brushless Motors 2 Left
2 24 Volt With 4 PM Motors Air Exchange Kit
3 24 Volt With 6 Brushless Motors 1 0 to 50%
4 24 Volt With 6 PM Motors 2 None
Evaporator Skins Kit 3 0 to 25%
1 Standard Cover (R10M) Controller Kit
2 Cover (R6.5M) 1 Micromax With GR60 Relay Board (right)
Evaporator Blower Kit Micromax Relay Board With CAN DATA
2 (right)
1 24 Volt With 6 Brushless Motors
2 24 Volt With 4 Brushless Motors 3 Micromax Relay Board
3 24 Volt With 6 PM Motors Micromax Relay Board With CAN DATA
4 (left)
Evaporator Refrigeration Kit
1 4 Row Coil Refrigeration Kit 5 Micromax With GR60 Relay Board (left)
2 5 Row Coil Refrigeration Kit
3 3 Row Coil Refrigeration Kit
Table 1-2 Option Table Refrigeration Kit
Connection Kit
Connection Kit
PID Condenser
PID Evaporator
Controller Kit
Electrical Kit
Air Exchange
Evaporator
Condenser
Evaporator
Evaporator
Condenser
Evaporator
Evaporator
Condenser
Blower Kit
Skins Kit
Skins Kit
AC353C
AC353E
In Dash
Fan Kit
MODEL
S/D
Kit
68AC353
-102 00001 00001 1 1 2 1 3 1 1 1 3 1

-102-1 00002 00002 1 2 1 1 1 1 1 1 3 2
-102-2 00003 00003 1 2 3 1 1 2 2 1 3 3
-102-3 00004 00004 1 2 3 1 1 2 2 1 3 4
-102-4 00005 00005 1 1 2 1 3 2 2 1 3 5
-102-5 00006 00006 1 1 4 1 3 2 2 1 3 5
-102-6 00007 00007 1 2 1 1 1 2 2 1 3 4
-102-7 00008 00008 1 2 1 1 1 2 2 1 3 3

Table 1-3 Additional Support Manuals
MANUAL/FORM NUMBER EQUIPMENT COVERED TYPE OF MANUAL
T-348PL 68AC353 Parts List
62-10699 Micromate Diagnostic Tool (Card)
7 8
6 9
4 5
2
12 Dash--Air
Option
11
1 10
13
1. Compressor 8. Main Harness

2. Discharge Check Valve 9. Driver Control
3. Refrigerant Lines 10. Power Harness
4. Compressor Harness 11. Main Circuit Breaker
5. Electronics Boards - Power Relay 12. Battery
6. Liquid Line Solenoid 13. Alternator
7. AC353 (Rooftop) See Figure 1-2
Figure 1-1 System Component Identification
1.4 GENERAL DESCRIPTION
1.4.1 Compressor Assembly refrigerant circuit. The high pressure switch contacts
The compressor assembly is mounted in the engine open on a pressure rise to shut down the system
when abnormally high refrigerant pressures occur.
compartment (see Figure 1-1) and includes the The electric unloaders provide a means of
refrigerant compressor, clutch assembly, suction and
discharge service valves, high pressure switch, low controlling compressor capacity, which enables
pressure switch, suction and discharge servicing control of temperature inside the bus. For more
(charging) ports and electric solenoid unloaders. detailed information on the 05G compressor, refer
to the Operation and Service Manual number
The compressor raises the pressure and temperature 62-02756.
of the refrigerant and forces it into the condenser 1.4.2 Discharge Check Valve
tubes. The clutch assembly provides a means of belt
driving the compressor by the bus engine. The A check valve is located in the discharge line close to
suction and discharge service valves enable servicing the compressor. (see Figure 1-1) The discharge
of the compressor. Suction and discharge servicing check valve is a spring loaded, normally closed valve
(charging) ports mounted on the service valves that opens with the flow of refrigerant from the
enable connection of charging hoses for servicing of compressor. When the compressor clutch is
the compressor, as well as other parts of the disengaged, the discharge check valve will close,

preventing the flow of high pressure liquid from the Micromax electronics, and the Fresh Air System. All
condenser back into the compressor. components are accessible by lifting the condenser
1.4.3 Rooftop Unit and evaporator top covers. Descriptions of the
The Rooftop unit (see Figure 1-2) is comprised of systems are provided in the following sub
the condensing section, evaporator section, paragraphs.
1
6
1. Top Cover, Condenser 4. Evaporator Section (See Figure 1-4)

2. Top Cover, Evaporator 5. Hinge, Evaporator Cover
3. Condenser Section (See Figure 1-3) 6. Condenser Fan Grille
Figure 1-2 Rooftop Unit Components

1.4.4 Condensing Section
The condensing section (Figure 1-3) includes the the tubes; this results in condensation of the
cover, left and right condenser coils, fan and motor refrigerant into a liquid.
assemblies, receiver, service valves and an ambient The receiver collects and stores liquid refrigerant.
temperature sensor.. The receiver is also fitted with a fusible plug which
High pressure high temperature refrigerant gas from protects the system from unsafe high pressure
the compressor passes thru the shipping shut-off conditions and liquid level sight glasses to determine
valves to the condenser coils. proper refrigerant liquid level.
The condenser coils provide heat transfer surface for The liquid refrigerant then passes thru the liquid line
condensing refrigerant gas at a high temperature and charge isolation valve to the evaporator.
pressure. The condenser fans circulate ambient air An ambient temperature sensor measures ambient
across the outside of the condenser tubes at a temperature and sends an electrical signal to the
temperature lower than refrigerant circulating inside controller.
PID
Model/Serial
Number Tag
7
4
1 8
3
2
1. Coil Assembly 5. Liquid Line

2. Receiver 6. Condenser Fan and Motor Assembly
3. Charge Isolation Valve 7. Ambient Temperature Sensor
4. Discharge Line. 8. Shipping Shut-off Valves
Figure 1-3 Condensing Section Components

1.4.5 Evaporator Section
The evaporator section (Figure 1-4) includes the filter-drier removes moisture and debris from the
evaporator coils, six blower and motor assemblies, liquid refrigerant before it enters the thermostatic
evaporator coil assemblies, heater coil assemblies, expansion valve in the evaporator assembly. Service
filter drier, a thermostatic expansion valve, liquid line valves enable isolation of the filter-drier for service.
solenoid, service valves and condensate drain The thermostatic expansion valve meters flow of
connections. refrigerant entering the evaporator coils. The liquid
The evaporator coils provide heat transfer surface line solenoid valve closes when system is shut down
for transferring heat from air circulating over the to prevent flooding of the evaporator coils with
outside coil area to the refrigerant circulating inside liquid refrigerant.
the tubes; thus providing cooling. The heating coils
provide heat transfer surface for transferring heat A heat valve controls the flow of engine coolant
from engine coolant water circulating inside the water to the heating coils upon receipt of a signal
tubes to air circulating over the outside surface of the from the controller. The condensate drain
tubes, thus providing heating. The fans circulate the connections provide a means for connecting tubing
air over the coils. The air filters remove dirt particles for disposing of condensate collected on the
from the air before it passes over the coils. The evaporator coils during cooling operation.
3
13 6
5
10
1 12
2
4
11
9
8
7
PID
Model/Serial
Number Tag
1. Evaporator Coil Assembly 8. Discharge Line

2. Heat Coil 9. Service Valve
3. Evaporator Return Air Filter 10. Liquid Line Solenoid
4. Expansion Valve 11. Heat Line Connection
5. Filter Drier 12. Control Panel
6. Blower & Motor Assembly 13. Fresh Air Damper
7. Suction Line
Figure 1-4 Evaporator Section Components
1.4.6 Fresh Air System

The Fresh Air System consists of a damper and controlled by the driver, if a switch is provided. In the
damper operator. The damper operator may be automatic mode, it is controlled by the Micromax to

open and close the damper to allow addition of fresh 1.5 REFRIGERATION SYSTEM COMPONENT SPECIFI-
air into the air entering the evaporator coil. For CATIONS
additional information on air flow, refer to paragraph a. Refrigerant Charge
1.9.
R-134a15.8 Lb (7.17 kg)
1.4.7 System Operating Controls And Components b. Compressor
UNIT MODEL AC353
The system is operated by a Mobile Climate Control
Micromax microprocessor controller which consist Compressor 05G
of a relay board (Figure 1-11), logic board No of Cylinders 6
(Figure 1-10), and manual operator switches. The Weight - Dry 145 lbs
manual operating switches are located on the drivers W/Clutch (65.77 kg)
control and may consist of a single OEM supplied Oil Charge 5.5 pints
ON/OFF switch, additional OEM supplied switches (2.6 liters)
or a Mobile Climate Control supplied Micromate Oil Level: Level in sight glass between Min.-Max marks on
control panel (Figure 1-14). The logic board compressor crankcase (curbside)
regulates the operational cycles of the system by Approved Compressor Oils - R-134a:
energizing or de-energizing relays on the relay board Castrol: Icematic SW68C
in response to deviations in interior temperature. Mobil: EAL Arctic 68
Modes of operation include Cooling, Heat and Vent. ICI: Emkarate RL68H
On systems fitted with only an ON/OFF switch and c. Thermostatic Expansion Valve:
on systems with the Micromate set in the AUTO Superheat Setting: 12 ±2°F (6.7 ±1°C)
mode, the logic board will cycle the system between
the operating modes as required to maintain desired d. High Pressure Switch (HPS):
set point temperature. Opens at: 350 ±10 psig (23.81 ±0.68bar)
Closes at: 250 ±10 psig (13.61 ±0.68bar)
In the vent mode the evaporator fans are operated to e. Low Pressure Switch (LPS)
circulate air in the bus interior.
Opens at: 6 ±3psig (0.41 ±0.20 bar)
In the heat mode the heat valve is opened to allow a Closes at: 25 ±3 psig (1.7 ±0.20 bar)
flow of engine coolant through the heat coils of the f. Water Temperature Switch (WTS)
evaporator coil. The evaporator fans operate to Bus manufacturer supplied - suggested close on tempera
circulate air over the evaporator coil in the same ture rise at 105°F (41°C).
manner as the vent mode.
1.6 ELECTRICAL SPECIFICATIONS - MOTORS
In the cooling mode the compressor is energized a. Evaporator Fan Motor
while the evaporator and condenser fans are
operated to provide refrigeration as required. The Permanent
Brushless Magnet
compressor is fitted with cylinder unloaders to Evaporator Motor
match compressor capacity to the bus requirements. 24 VDC
Once interior temperature reaches the desired set Horsepower (kW) 0.53/0.39 0.4/0.3
point, the system may operate in the clutch cycle or Full Load Amps (FLA) 15.2 11.0
reheat mode. A controller programmed for clutch Operating Speed (RPM) 3830 3013
cycle will de-energize the compressor clutch and
Bearing Lubrication Factory Lubricated
allow the system to operate in the vent mode until (additional grease not required)
further cooling is required. A controller
programmed for reheat will maintain compressor b. Condenser Fan Motor
operation and open the heat valve to allow reheating Permanent
Brushless Magnet
of the return air. In the reheat mode interior Condenser Motor
temperature is maintained at the desired set point 24 VDC
while additional dehumidification takes place. Horsepower (kW) 0.24/0.18 0.25/0.20
Full Load Amps (FLA) 7.0 7.2
Controls may also be provided to allow manual
operation of the evaporator fans in low or high speed Operating Speed (RPM) 2840 1900
and manual control of the fresh air damper in the Bearing Lubrication Factory Lubricated
open or closed position. (additional grease not required)

1.7 ELECTRICAL SPECIFICATIONS - SENSORS AND b. Fuses and Circuit Breakers
TRANSDUCERS The system is protected against high current by an
a. Suction and Discharge Pressure Transducer OEM supplied 125 amp fuse or circuit breaker.
Supply Voltage: 4.5 to 5.5 vdc (5 vdc nominal) Independent fuses or circuit breakers protect each
Supply current: 8 mA maximum evaporator blower motor and condenser motor
Output Range: 8K ohms minimum assembly. 5 amp fuses protect each relay board
Input Range: -6.7 to 450 psig (-0.46 to 30.62 bar) output, 10 amp fuses protect ignition circuit output.
c. Ambient Lockout
b. Temperature Sensors
Input Range: -52.6 to 158°F (-47 to 70°C) The ambient temperature sensor located in the
Output: NTC 10K ohms at 77°F (25°C) condenser section measures the condenser inlet air
temperature. When the temperature has fallen below
1.8 SAFETY DEVICES the cut out set point the compressor is locked out
System components are protected from damage until the temperature rises above the cut in setting.
caused by unsafe operating conditions with safety The set points will be programmed to cut out at 45°F
devices. Safety devices with Mobile Climate Control 〈7.2°C) and cut in at 50°F 〈10°C). This setting
supplied equipment include high pressure switch protects the compressor from damage caused by
(HPS), low pressure switch (LPS), circuit breakers operation at low pressures.
and fuses. d. Water Temperature Switch (WTS)
a. Pressure Switches
High Pressure Switch (HPS) When the the engine coolant temperature has fallen
below the cut out set point, the evaporator fans are
During the A/C mode, compressor operation will locked out until the temperature rises above the cut
automatically stop if the HPS switch contacts open in set point. The set point will be programmed to cut
due to an unsafe operating condition. Opening HPS in at 105°F (41°C).
contacts de-energizes the compressor clutch
shutting down the compressor. The high pressure
switch (HPS) is installed in the center head of the
compressor.
Low Pressure Switch (LPS)
The low pressure switch is installed in the
compressor and opens on a pressure drop to shut
down the system when a low pressure condition
occurs. In addition, if the microprocessor monitors a
pressure less than 10 psig (0.68 bar)by the suction
pressure transducer mounted in the evaporator
section, the system will be shut down for at least one
minute.

1.9 AIR FLOW
The paths for ambient air through the condenser and
coach air through the evaporator are illustrated in
Figure 1-5.
COIL RETURN
EVAPORATOR COIL EVAPORATOR COIL
AIR FILTERS
HEATER COIL HEATER COIL
FRESH AIR
COACH RETURN
AIR FILTER
EVAPORATOR
Return To Ambient
From Ambient Through Fan Through Fan From Ambient
Through Condenser CONDENSER Through Condenser
Figure 1-5 System Air Flow

1.10 AIR CONDITIONING REFRIGERATION CYCLE
When air conditioning (cooling) is selected by the the refrigerant enters the filter-drier where an
controller, the unit operates as a vapor compression absorbent keeps the refrigerant clean and dry.
system using R-134a as the refrigerant (See
Figure 1-6). The main components of the system are From the filter-drier, the liquid refrigerant then flows
the reciprocating compressor, air-cooled condenser through the liquid line service valve to the
coils, receiver, filter-drier, thermostatic expansion thermostatic expansion valve. The liquid line is
valve, liquid line solenoid valve and evaporator coils. equipped with a sight glass to observe the refrigerant
for restricted flow. The thermostatic expansion valve
The compressor raises the pressure and the reduces pressure and temperature of the liquid and
temperature of the refrigerant and forces it into the meters the flow of liquid refrigerant to the
condenser tubes. The condenser fan circulates evaporator to obtain maximum use of the
surrounding air (which is at a temperature lower than evaporator heat transfer surface.
the refrigerant) over the outside of the condenser
tubes. Heat transfer is established from the The low pressure, low temperature liquid that flows
refrigerant (inside the tubes) to the condenser air into the evaporator tubes is colder than the air that is
(flowing over the tubes). The condenser tubes have circulated over the evaporator tubes by the
fins designed to improve the transfer of heat from evaporator fans. Heat transfer is established from the
the refrigerant gas to the air; this removal of heat evaporator air (flowing over the tubes) to the
causes the refrigerant to liquefy, thus liquid refrigerant (flowing inside the tubes). The
refrigerant leaves the condenser and flows to the evaporator tubes have aluminum fins to increase
receiver. heat transfer from the air to the refrigerant; therefore
The receiver serves as a liquid refrigerant reservoir so the cooler air is circulated to the interior of the bus.
that a constant supply of liquid is available to the Liquid line solenoid valve closes during shutdown to
evaporators as needed and acts as a storage space prevent refrigerant flow.
when pumping down the system. The receiver is The transfer of heat from the air to the low
equipped with two sight glasses to observe temperature liquid refrigerant in the evaporator
refrigerant charge level. causes the liquid to vaporize. This low temperature,
The refrigerant leaves the receiver and passes low pressure vapor passes through the suction line
through the charge isolation valve to the liquid line and returns to the compressor where the cycle
solenoid valve. From the liquid line solenoid valve repeats.

Legend 22
Discharge 23 CONDENSER
Liquid
21
Suction
Refrigerant Flow
24
1. Discharge Service Valve

2. Discharge Check Valve
3. Service Port, Discharge 20 20
4. High Pressure Switch
5. Discharge Pressure Transducer
6. Low Pressure Switch (Crankcase)
7. Dash Air Liquid Line (Option)
8. Suction Service Valve/Port
9. Dash Air Suction Tee (Option)
10. Suction Pressure Transducer
11. Evaporator Coil
12. Thermal Expansion Valve (TXV) 19
13. TXV Bulb 19
14. TXV Equalizer Line
15. Liquid Line Solenoid Valve EVAPORATOR
16. Filter Drier
17. Liquid Line Service Valve
18. Liquid Line Sight Glass 15
19. Shipping Shut-off Valves
20. Condenser Coil
21. Receiver 16
22. Refrigerant Sight Glass
23. Fusible Plug
24. Charge Isolation Valve 17
18 14
11 12 11
2 5 13
3
4
1
6
10 7
9
8
Figure 1-6 Refrigerant Flow Diagram

1.11 HEATING CYCLE
Heating circuit (See Figure 1-6) components is circulated through the heating circuit by the engine
furnished by Mobile Climate Control include the and an auxiliary boost water pump. When the heat
heater coils and a solenoid operated heat valve. valve solenoid is energized, the valve will open to
Components furnished by the bus manufacturer allow engine coolant to flow through the heater coil.
include auxiliary heater and boost water pump. The The valve is normally closed so that if a failure occurs,
controller automatically controls the heat valve the system will be able to cool.
during the heating and reheat modes to maintain
required temperatures inside the bus. Engine coolant
LEGEND
COOLANT HEAT VALVE (Normally Closed)
INLET
OUTLET
BOOST
PUMP
EVAPORATOR
AC 353
MAIN ENGINE /
RADIATOR
Figure 1-7 Heat Flow Diagram

1.12 CONTROL PANEL WITH GR60 RELAY BOARD
2 1 5
1. Logic Board (See Figure 1-10) 4. Fresh Air

2. Relay Board - GR60 (See Figure 1-11) 5. Terminal Block (TB)
3. Power Relay (ON)
Figure 1-8 Control Panel

1.13 CONTROL PANEL
With CAN With/Out CAN
9 5 3 2 1 8
4
7
1. Logic Board (See Figure 1-10) 5. Fuses

2. Relay Board (See Figure 1-12) 6. Fresh Air
3. Logic Board, Data Communications 7. Power Terminal Block (PTB)
(See Figure 1-13 8. Terminal Block (TB)
4. Power Relay (ON) 9. Ground
Figure 1-9 Control Panel

1.14 LOGIC BOARD
J3
J
7
J4
J7
J6
J8
J2
J
5
J1
J1 Logic board power in. J7 Diagnostics interface (RS232, DB9).

J2 Micromate Display interface. J8 Not used
J3 Manual control inputs. D2 Blinks once per second in normal operation.
J4 Interlock Inputs On steady to indicate alarms detected.
(WTS, low side pressure switch etc.) D3 Off In normal operation, blinks out alarm
J5 Relay board interface. codes (2 digits each) when alarms detected.
J6 Sensor inputs (Thermistors, etc.). A-P Configuration Jumpers
Figure 1-10 Logic Board

1.15 RELAY BOARD - GR60, 24VDC
Figure 1-11. Relay Board - GR60

K1 Energizes evaporator fans 1 & 2 in high speed K12 Connects the negative side of condenser fan
or evaporator fans 1,2,3 & 4 in low speed. 5 to ground in high speed. Connects the
K2 Energizes evaporator fans 3 & 4 in high speed negative side of condenser fan 5 to
(not energized in low speed). the positive side of condenser fan 6 in
K3 Energizes evaporator fan 5 in high speed or low speed.
evaporator fans 5 & 6 in low speed. K13 Energizes the A/C clutch & liquid solenoid
K4 Energizes evaporator fan 6 in high speed (not valve (LSV).
energized in low speed). K14 Energizes unloader 1.
K5 Connects the negative side of evaporator fans K15 Energizes unloader 2.
1 & 2 to ground in high speed. Connects the K16 Energizes the fresh air damper.
negative side of evaporator fans 1 & 2 to K17 Energizes the heat solenoid valve (HSV).
positive side of evaporator fans 3 & 4 in K18 Energizes the A/C fault light output.
low speed
K19 Energizes the boost pump.
K6 Connects the negative side of evaporator fan
K20 Energizes the floor blower output.
5 to ground in high speed. Connects the
K21 Is energized by the logic board to turn the
negative side of evaporator fan 5 to
evaporator fans on high. The contacts of this
positive side of evaporator fan 6 in
relay energize the coils of relays K1, K2,
low speed
K3 & K4.
K 7 Energizes condenser fans 1 & 2 in high speed
or condenser fans 1,2,3 & 4 in low speed K22 Is energized by the logic board to turn the
K 8 Energizes condenser fans 3 & 4 in high speed evaporator fans on low. The contacts of this
(not energized in low speed). relay energize the coils of relays K1, K3,
K 9 Energizes condenser fan 5 in high speed or K5 & K6.
condenser fans 5 & 6 in low speed. K23 Is energized by the logic board to turn the
K10 Energizes condenser fan 6 in high speed condenser fans on high. The contacts of this
(not energized in low speed). relay energize the coils of relays K7, K8,
K11 Connects the negative side of condenser fans K9 & K10.
1 & 2 to ground in high speed. Connects the K24 Is energized by the logic board to turn the
negative side of condenser fans 1 & 2 to condenser fans on low. The contacts of this
the positive side of condenser fans 3 & 4 in relay energize the coils of relays K7, K9,
low speed. K11 & K12.

Figure 1-11. Relay Board - GR60 (Continued)
1.15 RELAY BOARD - GR60, 24VDC (Continued)

e. Thermal Circuit Breakers g. LEDS
CB 1 Evaporator Fan #1. 15 Amp. D 2 Relay K1 output active (evaporator fans 1,2,3 &
CB 2 Evaporator Fan #2. 15 Amp. 4 energized)
CB 3 Evaporator Fan #3. 15 Amp. D 6 Will be brightly lit if evaporator fans 1, 2, 3 & 4
CB 4 Evaporator Fan #4. 15 Amp. are on high. Will be at half intensity of they are on low.
CB 5 Evaporator Fan #5. 15 Amp.
D14 Relay K3 output active (evaporator fans 5 & 6
CB 6 Evaporator Fan #6. 15 Amp.
energized).
CB 7 Condenser Fan #1. 15 Amp.
CB 8 Condenser Fan #2. 15 Amp. D17 .Will be brightly lit if evaporator fans 5 &6 are
CB 9 Condenser Fan #3. 15 Amp. on high. Will be at half intensity of they are on low.
CB10 Condenser Fan #4. 15 Amp. D26 Relay K7 output active (condenser fans 1, 2, 3
CB11 Condenser Fan #5. 15 Amp. & 4 energized).
CB12 Condenser Fan #6. 15 Amp. D30 Will be brightly lit if condenser fans 1, 2, 3 & 4
CB13 A/C clutch, Unloaders 1&2, are on high. Will be at half intensity of they are on low.
Fresh air damper, Heat valve,
D38 Relay K9 output active (condenser fans 5 & 6
Fault output and Spare
energized).
output. 15 Amp
D41 Will be brightly lit if condenser fans 5 &6 are on
f. Connectors
high. Will be at half intensity of they are on low.
EF1--EF6 Evaporator fans.
CF1--CF4 Condenser fans. D51 A/C clutch, liquid solenoid valve output active.
JP1 External evaporator & condenser fan D54 Unloader 1 output active.
thermal overload connections. D57 Unloader 2 output active.
JP2 Logic board connector. D60 Fresh air output active.
JP3 Boost pump.
D63 Heat solenoid valve output active.
JP4 A/C clutch, fault output, compressor high
pressure switch. D66 A/C fault output active.
JP5 Spare output, fresh air output, heat valve. D69 Boost pump output active.
JP6 Unloaders 1 & 2. D72 Floor blower output active.

1.16 RELAY BOARD, 24VDC
Figure 1-12. Relay Board
a. Relays d. LEDS
K1 Energizes evaporator fans in low speed D 2 Evaporator fans output active -- high
K2 Energizes evaporator fans in high speed speed
(not energized in low speed). D 6 Evaporator fans output active.
K 7 Energizes condenser fans in low speed D26 Condenser fans output active.
K 8 Energizes condenser in high speed D30 Condenser fans on high speed
(not energized in low speed). D51 A/C clutch and liquid line solenoid valve
K13 Energizes the A/C clutch and liquid line output active.
solenoid valve. D54 Unloader 1 output active.
K14 Energizes unloader 1. D57 Unloader 2 output active.
K15 Energizes unloader 2. D63 Heat output active (RCV).
K16 Energizes fresh air damper. D66 Fault output active.
K17 Energizes reheat coolant valve. D69 Boost pump output active.
K18 Energizes the fault light output. D72 Driver’s liquid line solenoid valve active.
K19 Energizes the boost pump. D17 Fresh air relay fuse out.
K20 Energizes the driver’s liquid line solenoid D38 Unloader 1 relay fuse out.
valve. D18 Evaporator fan motor relay fuse out.
b. Connectors D68 Fault light out relay fuse out.
JA Relay board connector(communication D47 Unloader 2 relay fuse out.
to system). D61 Heater relay fuse out.
JB Boost pump. D90 Clutch relay fuse out.
JC Ribbon Cable (Logic Module to Relay D77 Unloader 1 fuse out.
Board) D31 Condenser motor fan relay fuse out.
c. Fuses D83 Boost pump relay fuse out.
F1 Fresh air relay.
F2 Unloader 1 relay.
F3 Evaporator fan motor relay.
F4 Fault light out relay.
F5 Unloader 2 relay.
F6 Heater relay.
F7 Clutch relay.
F8 Spare.
F9 Condenser motor fan relay.
F10 Boost pump relay.

1.17 LOGIC BOARD, DATA COMMUNICATIONS
1 8
9 15
16 23
Pin Function Remarks Pin Function Remarks

1 +24VDC In Power In 13 RS--232 TXD HVAC Data Port
2 24VDC Return Ground 14 RS--232 RXD HVAC Data Port
3 Alt, CAN_H CAN Port #2 (Optional) 15 LED Out Status Indicator (Optional)
4 Alt, CAN_L CAN Port #2 (Optional) 16 N/C
5 N/C 17 N/C
6 N/C 18 RS--232 Gnd HVAC Data Port
7 N/C 19 N/C
8 LED Gnd Status Indicator (Optional) 20 N/C
9 CAN_H J1939 Port 21 N/C
10 CAN_L J1939 Port 22 N/C
11 N/C 23 N/C
12 N/C
Figure 1-13 Logic Board, Data Communications

1.18 CONTROL PANEL (Diagnostic Module)
1 2 3 4 5 6
11 10 9 8
1. Display 7. HEAT (Only) Button

2. DOWN Button - decrease selection 8. FAN SPEED Button
3. UP Button - increase selection 9. FRESH AIR Button
4. VENT (Only) Button 10. TEMPERATURE (Inside / Outside)
5. AUTO Button (Automatic Control) Button
6. COOLING (Only) Button 11. ON/OFF Button
Figure 1-14 Micromate Control Panel

SECTION 2
OPERATION
2.1 STARTING, STOPPING AND OPERATING INSTRUC- Figure 1-14) to illuminate the indicator light and
TIONS place the system in that mode of operation.
2.1.1 Power to Logic Board 4. If low or high speed evaporator fan speed is de
sired, press the FAN SPEED button to illuminate
Before starting, electrical power must be available the indicator light and bring speed to the desired
from the bus power supply. The system components level.
receive power from two sources:
5. To open or close the fresh air damper (if sup
a. 24 vdc power for the microprocessor electronics is plied), press the FRESH AIR button to illuminate
supplied through the bus interface. the indicator light and bring the damper to the de
b. 24 vdc, 125 amp, power from a circuit breaker in sired position.
the battery compartment supplies power for the 6. To read interior or exterior temperature, press the
clutch, compressor, unloader solenoids, evapora TEMPERATURE button to illuminate the indi
tor and condenser assemblies; this power is con cator light and bring the display to the desired
trolled by the Logic Board. temperature reading. After a short delay, the dis
2.1.2 Starting play will return to the default set point or return
air temperature reading.
a. If the engine is not running, start the engine.
7. Setpoint may be changed by pressing the UP or
b. OEM SUPPLIED SWITCHES DOWN arrow button. The UP button will in
Actual start sequence depends on the operating crease the setpoint temperature and the DOWN
controls supplied. If only an ON/OFF switch is button will decrease the setpoint temperature.
supplied, placing the switch in the ON position
will start the system. 8. For additional Micromate operating data refer to
paragraph 2.4.
c. MICROMATE CONTROL PANEL
It is suggested the system be started in the auto 2.1.3 Self-Test and Diagnostics (Check for Errors
matic mode. and/or Alarms)
1. The Micromate Control Panel Display (see Self-test of the main Logic Board electrical circuit is
Figure 1-14) may be programmed to display the automatically initiated when the system is powered
set point temperature or return air temperature. up. If there is an error in the circuit, an alarm will be
To determine which display temperature is pro indicated by flashing LED's on the Logic Board. If a
grammed, press the TEMPERATURE button so Micromate is connected to the Logic Board, the
that the OUT SIDE AIR indicator is illuminated. error code can also be read on the display. If there are
If the controller cycles back to the INSIDE AIR no errors in the circuit, system will operate normally
indicator, then the controller is programmed to and flash the status LED at a one second interval.
display return air temperature. If the controller During normal operation, the Logic Board monitors
does not automatically cycle back to the return air system operating parameters for out of tolerance
indicator, then the controller is programmed to conditions. If an out of tolerance condition occurs,
display set point temperature. ALARM will be indicated through the code LED or
on the Micromate display. Refer to section 3 for
2. To start the system, press the I/O button to illu definition of system errors and alarms and general
minate the indicator light and signal the Logic troubleshooting procedures.
Board to perform start up. Ensure the AUTO
button indicator is illuminated. If not, press the 2.1.4 Stopping
AUTO button to place the system in the automat Placing the ON/OFF switch in the OFF position or
ic mode. After the pre-trip inspection is com pressing the Micromate ON/OFF button will stop
pleted, the switches may be set in accordance with the system operation by removing power to the
the desired control modes. Logic Board. Note: If OEM switches at the dash are
3. If cooling only, heating only or ventilation only is supplied, they will override control unless the J3 plug
desired, press the corresponding button (refer to on the logic board is disconnected.

2.2 PRE-TRIP INSPECTION of a logic board (Figure 1-10), relay board (Figure
1.15 or Figure 1.16), and manual operator switches.
After starting system, allow system to stabilize for ten The logic board regulates operational cycles of the
to fifteen minutes and check for the following: system by energizing or de-energizing Relay Board
a. Listen for abnormal noises in compressor or fan relays in response to deviations in interior
motors. temperature. Modes of operation include Cooling,
b. Check compressor oil level. (Refer to section Heat and Vent. Refer to Figure 2-1 and the following
4.15.4) paragraphs for a description of each mode.
c. Check refrigerant charge. (Refer to section 4.8.1) Figure 2-1 shows the Logic Board actions at various
d. Ensure that self-test has been successfully per temperature deviations from setpoint. On rising
formed and that there are no errors or alarms indi temperature, changes occur when the temperature
cated. (Refer to section 2.1.3.) rises above Logic Board setpoints, On falling
temperature, changes occur when temperatures falls
2.3 MODES OF OPERATION below Logic Board set point. The system will operate
The system is operated by a Mobile Climate Control in these modes unless pressures override the Logic
Micromax microprocessor controller which consists Board settings.
COOL
3°F HIGH SPEED 3°F
LOADED
COOL
2°F HIGH SPEED 2°F
4 CYLINDERS
COOL
1°F LOW SPEED 1°F
2 CYLINDERS
SETPOINT SETPOINT
REHEAT DUTY CYCLE VENT

--1°F 0--100% --1°F
LOW SPEED
4 CYLINDERS
--2°F --2°F
HEAT
--3°F --3°F
HEAT
LOW SPEED
--4°F --4°F
--5°F HEAT --5°F HEAT

HIGH SPEED HIGH SPEED
Cool Heat
Figure 2-1 Capacity Control Diagram

2.3.1 Temperature Control When operating in cooling, the unloaders are used to
reduce system capacity as return air temperature
Temperature is controlled by maintaining the return approaches set point. Operation of the unloaders
air temperature measured at the return air grille. balances system capacity with the load and thereby
2.3.2 Cooling Mode prevents overshoot from set point.
Cooling is accomplished by energizing the Relay Board mounted unloader outputs control the
compressor and condenser fans, opening the liquid capacity of the compressor by energizing or
line solenoid valve and closing the heating valve. de-energizing unloader solenoid valves. The model
Once interior temperature reaches the desired set 05G compressor has three banks of two cylinders
point, the system may operate in the clutch cycle or each. Energizing a valve de-activates a bank of
reheat mode. Selection of clutch cycle or reheat is cylinders. The outboard cylinder banks of the 05G
factory programmed in accordance with the bus are equipped with unloader valves (UV1 and UV2),
purchase specification. each controlling two cylinders; this allows the 05G to
be operated with two, four or six cylinders.
A controller programmed for clutch cycle will Whenever the compressor is started, the unloaders
de-energize the compressor clutch and allow the are energized for a preset delay time to reduce
system to operate in the vent mode until further starting torque. After the delay, unloaders may be
cooling is required. de-energized. Any subsequent changes between
A controller programmed for reheat will maintain energizing and de-energizing the unloaders for
compressor operation and cycle the heat valve to temperature control is also staged for a preset delay
allow reheating of the return air. In the reheat mode time. Once an unloader is energized for pressure
interior temperature is maintained at the desired set control, it remains energized for two minutes to
point while additional dehumidification takes place. prevent short cycling. Only one unloader may
change state at a time when staging is required.
2.3.3 Heating Mode Operating parameters for temperature control,
suction pressure control and discharge pressure
In the heat mode the liquid line solenoid is closed and control are as follows.
the compressor and condenser fans are shut down.
The heat valve is opened to allow a flow of engine a. Temperature Control
coolant through the heat section of the evaporator The unloaders are used to control system capacity by
coil. The evaporator fans speed is varied as required controlling compressor capacity.
to circulate air over the evaporator coil based on the
temperature difference from setpoint. 1. Compressor Unloader UV1 Relay. When return
air temperature falls to less than 2°F (1.1°C)
Operation in the heating mode is controlled by the above set point unloader UV1 is energized. If
water temperature switch (WTS). The WTS is temperature rises to greater than 3°F (1.7°C)
located on the engine block of the vehicle and is above set point, UV-1 will be de-energized to
provided by the OEM. It senses the engine coolant place the compressor at 100% capacity.
temperature and reverses its contacts on
temperature rise at 105°F. The switch prevents the 2. Compressor Unloader UV2 Relay. When return
circulation of cooler air throughout the vehicle as the air temperature falls to less than 1°F (0.6°C)
engine comes up to temperature. above set point unloader UV2 is energized. If
temperature rises to greater than 2°F (1.1°C)
2.3.4 Boost Pump above set point, UV-2 will be de-energized to
place the compressor at 66% capacity.
When the unit is in the heat mode, and if a boost
pump is supplied by the coach manufacturer, the b. Suction Pressure
boost pump relay is energized, providing 24 VDC to The unloaders are used to control suction pressure
activate the boost pump. and thereby prevent coil frosting:
2.3.5 Vent Mode 1. Compressor Unloader UV1 Relay. When the suc
In the vent mode the evaporator fans are operated to tion pressure decreases below 26 psig, unloader
circulate air in the bus interior. UV1 is energized unloading a cylinder bank (two
cylinders); this output will remain energized until
2.3.6 Compressor Unloader Control the pressure increases to above 34 psig.

2. Compressor Unloader UV2 Relay. When suction pressure decreases below 135 PSIG. High speed will
pressure decreases below 23 psig, unloader UV2 is also remain activated if a high pressure alarm has
energized unloading the second compressor cyl been activated and operation has not been locked
inder bank; this output will remain energized until out (refer to Table 3-2).
the pressure increases to above 31 psig. 2.3.9 Compressor Clutch Control
c. Discharge Pressure
A belt driven electric clutch is employed to transmit
Discharge pressure is also controlled by the engine power to the air conditioning compressor.
unloaders: De-energizing the clutch electric coil disengages the
1 Compressor Unloader UV1 Relay. When the dis clutch and removes power from the compressor.
charge pressure increases above set point A (see The clutch will be engaged when in cooling and
chart below), unloader UV1 is energized; this un disengaged when the system is off, in heating or
loader will remain energized until the pressure de during high and low pressure conditions.
creases below set point B (see chart below). The clutch coil will be de-energized if the discharge
Table 2-1. Unloader UV1 Relay pressure rises to the cutout setting of the compressor
mounted high pressure switch. An alarm will be
HPS Switch Set Point A Set Point B triggered if this condition exists for more than a 0.5
(PSIG) (PSIG) (PSIG) second. The clutch coil will energize when the
300 275 220 discharge pressure falls to the reset point of the high
2 Compressor Unloader UV2 Relay. On R-134a pressure switch.
systems when the discharge pressure increases The clutch coil will be de-energized whenever the
above set point A (see chart below), unloader suction pressure decreases below 10 PSIG, an alarm
UV2 is energized; this unloader will remain ener will be triggered if this condition exists for more than
gized until the pressure decreases below set point 10 seconds. The clutch coil will energize when the
B (see chart below). suction pressure rises to the reset point. If the alarm
is triggered 3 times in a 30 minute time period the
Table 2-2. Unloader UV2 Relay system will be locked out (See 3.2.1 Alarm Codes).
HPS Switch Set Point A Set Point B
(PSIG) (PSIG) (PSIG) The clutch coil is prevented from engagement when
300 285 225
the ambient temperature is below ambient lockout
setpoint.
2.3.7 Evaporator Fan Speed Selection 2.3.10 Liquid Line Solenoid Control
Temperature control is the primary method of The liquid line solenoid is energized (open) when the
determining the fan speed selection. Table 2-3 compressor clutch is energized and de-energized
indicates relay operational status for the various fan (closed) when the clutch is not.
motor states while Figure 2-1 provides Logic Board
speed selections at various deviations from set point.. 2.3.11 Alarm Description
Table 2-3 Evaporator Fan Speed Relay Operation Alarm descriptions and troubleshooting procedures
are provided in section 3.
STAT HIGH EVAP FAN 2.3.12 Hour Meters
E SPEED RELAY
RELAYS Hour meter readings are available in the parameter
Off Off Off code list of the Micromate. The hour meters record
Low Off On the compressor run time and the total time the
evaporator fans are on. The maximum hours are
High On On
999,999. Refer to paragraph 2.4.2 for instructions on
2.3.8 Condenser Fan Control reading parameter codes.
The condenser fans start in low speed when the 2.4 MICROPROCESSOR DIAGNOSTICS
compressor clutch output is energized. The fans will
switch to high speed when the discharge pressure The Micromate control panel allows the user to
reaches 190 psig (R-134a) and will remain energized interface with the microprocessor based control.
in high speed for a minimum period of 5 minutes. This allows system parameters, alarms and settings to
The fans will switch to low speed when discharge be viewed and modified.

2.4.1 Control NOTE
NOTE Be sure to reconnect J3 when testing is com
pleted or the system will fail to operate when
1. This procedure should be performed by the Micromate is disconnected.
an HVAC technician who has been
trained on Mobile Climate Control NOTE
system design. The control
When modifying the setpoint temperature
configuration is preset by the
manufacturer and resetting of the for diagnostic purposes, be sure to reset the
parameters should not be required. It is setpoint when testing is complete.
recommended that MCC Service or
2.4.2 Diagnostic Mode
Engineering is contacted before any
control configuration is changed. MCC The diagnostic mode can be entered by pressing the
can not be responsible for failures or UP and DOWN arrow keys simultaneously for 3
damage resulting from unauthorized seconds. The Micromate control panel display
screen will go blank for one second and then enter
changes. the alarm screen. The diagnostic mode allows alarms
and system parameters to be viewed. If there are any
2. If a replacement Logic Module is alarms stored, the most recent alarm will be shown.
installed, it is necessary to match the To exit the diagnostic mode, press the ON/OFF key
configuration jumpers (refer to once, or do not touch any keys for 30 seconds. To
Figure 1-10) to the original board. Refer view additional alarm information, refer to section 3.
to paragraph 4.19. 2.4.3 System Parameters
To view system parameters, first enter the
a. Turn the A/C main power switch (located in the Diagnostic Mode. Refer to paragraph 2.4.2. . The
driver's area) to OFF. parameters are shown in Table 2-5. While in the
diagnostic mode, press an UP or DOWN arrow key
b. Connect the Micromate control panel to the ser to switch the display to the Parameter Display. With
vice port (J2) located in the return air section. (re the first Parameter displayed, press the DOWN
fer to Figure 1-10) arrow key to scroll through the list from the first to
the last parameter or press the UP arrow to scroll
c. Unplug the logic board connector J3. from the last to the first parameter. When scrolling
d. Turn the A/C main power switch back to the ON through the parameters, the current parameter will
position. be displayed for two seconds. After two seconds, the
display will show the data for the current parameter.
e. Activate the system by pressing the I/O key on the When the last parameter is reached, the list will wrap
Micromate panel. back to P1.

2.4.4 Test Mode Table 2-4. Controller Test List
With the system in normal operation, the controller TEST OUTPUT STATE
may be placed in the test mode, by doing the T00 All Relays Off
following: T01 Evaporator Fans High On
a. Enter the diagnostic mode by pressing the UP and T02 Evaporator Fans Low On
DOWN arrow keys simultaneously for 3 seconds.
T03 Condenser Fans High On
b. Enter the test mode immediately by pressing the
COOL button five times. T04 Condenser Fans Low On
c. If an alarm is present, press the UP arrow key until Compressor & Liquid
T05 Line Solenoid On
“---” is displayed.
d. In the test mode, the display will read “T##” T06 Unloader Valve 1 On
where “##” indicated the test number that is cur T07 Unloader Valve 2 On
rently running. T08 Not Applicable On
e. The initial indication will be “T00”. This indicates T09 Reheat Coolant Valve On
the controller is in the test mode and all relays are T10 Fault On
de-energized. Press the DOWN arrow key to T11 Boost On
bring the Micromate to the next test screen and
energize the corresponding component(s). Press Spare/Motor Input/
T12 On
the UP arrow key move backwards through the Floor Blower
list. A listing of tests is provided in Table 2-4.
f. To terminate testing, press the I/0 key.

Table 2-5. Parameter Codes
CODE CODE NAME DESCRIPTION
P1 Return Air This value is the temperature measured by the return air sensor. If the sensor is shorted it
Temperature will display CL. If it is open circuited it will display OP.
P2 Coil Temperature Not used.
P3 Ambient Temperature This value is the outside temperature measured by the ambient temperature sensor. If the
sensor is shorted it will display CL. If it is open circuited it will display OP.
P4 Suction Line Not used.
Temperature
P5 Suction Pressure This value is the suction pressure measured by the suction pressure transducer. If the
sensor is shorted it will display CL If it is open circuited it will display OP.
P6 Discharge Pressure This value is the discharge pressure measured by the discharge pressure transducer. If
the sensor is shorted it will display CL and if it is open circuited it will display OP.
P7 Superheat Not used.
P8 Analog Set Point Not used.
Temperature
P9 A/C Control Window This is the number of degrees F above setpoint at which the unloaders will be both ener
#1 gized. This value can be modified between 0 and 10 degrees F. The default value is 1
degree F.
P10 A/C Control Window This is the number of degrees F above AC control window one at which the first unload
#2 er will be energized. This value can be modified between 0 and 10 degrees F. The default
value is 1 degree F.
P11 A/C Control Window This is the number of degrees F above AC control window two at which the evaporator
#3 fan speed will be set to low. This value can be modified between 0 and 10 degrees F.
The default value is 1 degree F.
P12 Heat Control Window This is the number of degrees F below setpoint before the reheat coolantvalve is energi
zed. This value can be modified between 0 and 10 degrees F. The default value is 2 de
gree F for heat and 4 degrees F for reheat.
P13 Compressor Safety Off This number is the minimum time in minutes that the compressor must be off after a
Delay high or low pressure alarm before it can be restarted. This value can be modified be
tween one and five minutes. The default value is 1.
P14 Fan Delay This is the minimum time (in seconds) that the fans must run at a particular speed before
changing to another speed. This value can be modified between one and 60 seconds. The
default value is two seconds.
P15 Reheat Valve Delay This is the minimum time (in seconds) that the reheat valve must be in a particular state
(open /closed) before changing to another state. This value can be modified between 1
and 60 seconds. The default value is 2 seconds.
P16 Compressor High Pres This is the current state of the compressor high pressure switch input. “CL” will be dis
sure Switch played if it is closed and “OP” will be displayed if it is open.
P17 Condenser Fan Speed Not used.
Switch
P18 Maximum Setpoint This is the maximum value that the operator will be allowed to set the setpoint tempera
ture. The value can be modified in degrees with the up and down keys to a value be
tween 60°F and 80°F.
P19 Minimum Setpoint This is the minimum value that the operator will be allowed to set the setpoint tempera
ture. The value can be modified in degrees with the up and down keys to a value be
tween 60°F and 80°F.

Table 2-5. Parameter Codes - Continued
Code Code Name Description
P20 Compressor Hours High This is the number of hours of operation that the compressor has run with the clutch
energized in thousands.
P21 Compressor Hours Low This is the number of hours of operation that the compressor has run with the clutch
energized in hundreds, tens and ones.
P22 Evaporator Hours High This is the number (in thousands) of hours of operation with the evaporator fans ener
gized.
P23 Evaporator Hours Low This is the number (in hundreds, tens and ones) of hours of operation with the evapora
tor fans energized.
P24 Maintenance 1 Hour This is the value of compressor hours high (P20) at which maintenance alarm #1 will be
High activated. This value can be modified by the up and down arrow keys. If both high and
low values are zero the alarm is disabled.
P25 Maintenance 1 Hour This is the value of compressor hours low (P21) at which maintenance alarm #1 will be
Low activated. This value can be modified by the up and down arrow keys. If both high and
low values are zero the alarm is disabled.
P26 Maintenance 2 Hours This is the value of evaporator fan hours high (P22) at which maintenance alarm #2 will
High be activated. This value can be modified by the up and down arrow keys. If both high
and low values are zero the alarm is disabled.
P27 Maintenance 2 Hours This is the value of evaporator fan hours low (P23) at which maintenance alarm #2 will
Low be activated. This value can be modified by the up and down arrow keys. If both high
and low values are zero the alarm is disabled.
P28 Freeze Alarm Setting This is the value at which the freeze alarm will be activated. The default value is 32°F.
This value can be modified between 20°F and 40°F in one degree increments by using
the arrow keys
P29 Relay Module Voltage This is the voltage being supplied to the relay module.
P30 Main Board Software This is the software version of the logic board.
Version
P31 Display Software This is the software version of the display module.
Version
P32 Ki Not used.
P33 Kp Not used.
P34 Heat Set Point Offset This value is the offset that can be used to change the points at which the unit switches
between heat and vent in the heat mode. A positive value will raise the critical tempera
tures (winter use) and a negative value will decrease the critical temperatures (summer
use).
P35 Default Display Temper This value determines what temperature value the driver's display will show as a default.
ature When the value is OFF, set-point temperature is displayed. When the value is ON, return
air temperature is displayed. This option is only available in logic module software revi
sions 1.9 and newer, and drivers display software revision 1.3 and newer. Otherwise P35
will not be active and set-point temperature will only be displayed as default.
P37 Seasonal Operation This is a binary (ON or OFF) parameter for seasonal operation. When it is turn ON, the
control will run automatic mode, and the Cool and Heat Mode input (J3-3 and J3-4) will
determine the temperature set point. When Cool Mode input J3-3 is energized, there will
be no offset for the set point. When Heat Mode input J3-4 is energized, the temperature
set point will be offset by the value of P34.
P38 Evaporator Fan Opera This is a binary (ON or OFF) parameter. When set to the OFF position, the evaporator
tion in Heat Mode blowers will operate according to the values set for Auto Mode. When set to ON, the
evaporator blowers will operate in low speed in Heat Mode.

Table 2-5. Parameter Codes - Continued
Code Code Name Description
P39 Compressor Minimum When parameter is set to OFF, the minimum compressor on time will be 5 minutes.
On time When set to ON, the minimum compressor on time will be 1 minute.
P40 Enable Hidden Alarm This value determines if alarms A33 and A34 are displayed. When the value is OFF,
alarms A33 and A34 will not be displayed. When the value is ON, alarms A33 and A34
will be displayed.
P41 Fresh Air Damper When the value is OFF, the fresh air damper will operate 5°F above or below the control
set point. When the value is ON, the fresh air damper will operate 2°F above or below
the control set point.
P42 Defrost Operation This value determines if the defrost switch will override the Micromate controller. If the
parameter is ON the defrost switch will initiate unit defrost whenever it senses a need for
defrosting (the Micromate display will shut off in defrost). If the parameter is OFF the
Micromate display will continue to operate and override the defrost switch.

SECTION 3
TROUBLESHOOTING
CAUTION
Do not under any circumstances attempt to service the microprocessor. Should a problem de
velop with the microprocessor, replace it.
3.1 SELF DIAGNOSTICS number of times that the Logic Board STATUS and
CODE LED's (see Figure 1-10) flash
A self test is performed by the Micromax Logic simultaneously. The Micromate control panel
Board each time the board is powered up. Errors, if display will indicate errors with the code ER-#,
any, will be indicated and the unit will not be allowed where “ER” is the error prefix and # is the error
to start. The error codes can be read by counting the number.
Table 3-1 Error Codes
CODE NAME DESCRIPTION
ER 1 Data Memory Logic board data memory failure.
ER 2 Program Memory Logic board program memory failure.
ER 3 A/D A/D and multiplexer failure.
ER 4 Communication Failure Failure in communication between the logic board and MDST.
ER 5 Program Memory Display program memory failure.
3.2 SYSTEM ALARMS VENT key to scroll back, only the alarm code will be
shown, the alarm time will not be shown. If the
3.2.1 Alarm Codes AUTO key is held down for five seconds while “---”
The Micromax Logic Board continuously monitors is displayed all inactive alarms are cleared. A listing of
system parameters and will generate an ALARM if a alarm codes is provided in Table 3-2.
parameter exceeds preset limits. Alarms are indicated 3.2.2 Activation
and the controller will respond in accordance with When alarms are detected, they are placed in an alarm
the information provided in Table 3-2. The alarm queue in the order at which they initiated unless the
codes can be read by counting the number of times alarm is already present. Each alarm recorded will
that the Logic Board CODE LED (see Figure 1-10) also capture an evaporator hour meter reading
flashes. Each alarm code is a two digit number, the corresponding to the activation time. If the AUTO
first set of flashes is the first digit and (after a slight key is pressed while an alarm is displayed, the
pause) the second set of flashes is the second digit. activation time capture will be shown.
The Micromate control panel display will indicate 3.2.3 Alarm Queue
alarms with the code A-## or i-##, where “A” is an The alarm queue consist of 10 alarm locations. When
active alarm prefix, “i” is an inactive alarm prefix and the alarm queue is full the Logic Board will take the
## is the alarm number. If no alarms are present, the required action but the alarm will not be recorded.
display will show “---”. To access the alarm codes, When this situation occurs, an “Alarm Queue
press the UP and DOWN arrow keys at the same Full”alarm will be generated. When the alarms are
time and hold for 3 seconds. If multiple alarms are viewed this will be the first alarm to be shown.
present the user can scroll through each alarm by
pressing the AUTO key. When the end of the alarm 3.2.4 Alarm Clear
list is reached the display will show “---”. Press The user may clear inactive alarms using the
VENT to scroll backward from the latest alarm to Micromate control panel keypad. Refer to paragraph
the earliest alarm in the queue. When using the 3.2.1.

3.2.5 Exit Alarm Queue 9. If no digits are streamed, STOP. The Micromate
To exit the alarm queue press the ON/OFF key Logic unit or the interface connection is defect
once, or if no key is pressed for 30 seconds it will reset ive.
to normal mode. 10.Connect the RS232 USB cable to the Gateway
3.3 TROUBLESHOOTING RS232 connector.
General procedures for system troubleshooting are 11.The following 3 repeating streams should be
provided in Table 3-3 shown.
3.3.1 Troubleshooting No CAN Communication
T18FFDD1980000000000000000
Follow these steps: T18FFDE1980000000000000000
1. Connect the Micromate display unit. T18FFDD19800FF00000000FFFF
2. Check that the parameters are displayed by the T18FFDD1980000000000000000
Micromate display unit. T18FFDE1980000000000000000
3. If no parameters are displayed, STOP. The Mi T18FFDD19800FF00000000FFFF
cromate logic unit is bad.
4. Use an RS232 USB cable to connect a laptop USB
port to the Micromate Logic unit. 12.If no 3 repeating streams are shown, STOP. The
Gateway unit is bad.
5. Launch HyperTerminal software by clicking on
“start\
All Programs\accessories\communications\Hy
perTerminal”.
6. With the Caps Lock set, press the “S” and “5”
keys in unison, then press “Enter”.
7. With the Caps Lock set, press “O” and press
“Enter”.
8. A stream of five 2 digit numbers starting with
“3D”should be shown.
3D 00 E6 DD 5C
3D 00 FF C4 41
3D 00 EB D8 35

Table 3-2 Alarm Codes
ALARM TITLE CAUSE REMEDY CONTROLLER
NO. RESPONSE
A11 Coil Freeze Coil temperature is less Check causes of coil An alarm will be generated
than 32°F and the com freezing. (Refer to sec and the system will shut
pressor is operating. tion 3.3.7) down. The evaporator fans
will remain running while
the compressor is off.
A12 High Voltage The battery voltage is Check, repair or replace The system is shut down
greater than 32 volts. alternator. until the voltage returns to
normal levels.
A13 Low Voltage The battery voltage is Check, repair or replace The system is shut down
less than 17 volts. wiring or alternator. until the voltage returns to
normal levels.
A14 Return Air Probe Failure Return air temperature Ensure all connectors are All outputs except the evap
sensor failure or wiring plugged in. Check sensor orator fans will be de-ener
defective. resistance or wiring. Re gized.
fer to paragraph 4.16.
Replace sensor or repair
wiring.
A15 Suction Pressure Suction pressure trans Ensure all connectors are Both unloaders are ener
Transducer Failure ducer failure or wiring plugged in. Check sensor gized.
defective. voltage or wiring. Re
place sensor or repair
wiring.
A16 Discharge Pressure Discharge pressure trans Ensure all connectors are One unloader is energized.
Transducer Failure ducer failure or wiring plugged in. Check sensor Condenser fans will run on
defective. voltage or wiring. Re high speed.
place sensor or repair
wiring.
A17 Low Pressure Shutdown Low suction pressure Check cause of low suc The clutch is de-energized
switch open or wiring tion pressure. (Refer to for the minimum off time.
defective. section 3.3.4) The evaporator fans will re
main running during this
period. After the compres
sor cycles off three times in
30 minutes all outputs will
be de-energized (except for
the evaporator fans and
heat) and the system is
locked out until the power
is cycled or the alarm is re
set.
A21 High Discharge Pressure High discharge pressure Check discharge pressure The clutch is de-energized
switch open or wiring transducer reading, wir for the minimum off time.
defective. ing or cause of high dis The condenser and evapo
charge pressure. (Refer rator fans will remain run
to section 3.3.4) ning during this period. Af
ter the compressor cycles
off three times in 30 min
utes all outputs will be de-
energized (except for the
evaporator fans and heat)
and the system is locked out
until the power is cycled or
the alarm is reset.

Table 3-2. Alarm Codes - Continued
ALARM TITLE CAUSE REMEDY CONTROLLER
NO RESPONSE
A22 Breaker Trip/Blown Fuse A breaker/fuse on the Check breakers/fuse for Alarm will be generated.
Alarm relay board has tripped tripped device. Repair
or a fan relay has failed. short and reset/replace
breaker/fuse.
A23 Evaporator Fan Overload Evaporator fan overload Ensure connector is Alarm will be generated.
jumper is open. plugged in or repair
wiring.
A24 Condenser Fan Overload Condenser fan overload Ensure connector is Alarm will be generated.
jumper is open. plugged in or repair
wiring.
A25 Not used
A26 Not used
A31 Maintenance Alarm 1 The compressor hour Reset the maintenance Alarm will be generated.
meter is greater than the hour meter.
value in Maintenance
Hour Meter 1.
A32 Maintenance Alarm 2 The evaporator hour me Reset the maintenance Alarm will be generated.
ter is greater than the hour meter.
value in Maintenance
Hour Meter 2.
A33 Low Pressure Warning Suction pressure low Check cause of low suc Alarm will be generated.
enough to energize UV2. tion pressure. (Refer to
section 3.3.4)
A34 High Pressure Warning Discharge pressure high Check cause of high dis Alarm will be generated.
enough to charge pressure. (Refer
energize UV2. to section 3.3.4)
A99 Alarm Queue Full All locations of the alarm Record and clear alarm Alarm will be generated.
queue are currently full queue.
and no more alarms can
be saved.

Table 3-3. General System Troubleshooting Procedures
INDICATION/ REFERENCE
TROUBLE POSSIBLE CAUSES SECTION
3.3.2 System Will Not Cool
Compressor will not run Active system alarm 3.2
V-Belt loose or defective Check
Clutch coil defective Check/Replace
Clutch malfunction Check/Replace
Compressor malfunction See Table 1-3
Electrical malfunction Coach power source defective Check/Repair
Circuit Breaker/safety device open Check/Reset
3.3.3 System Runs But Has Insufficient Cooling
Compressor V-Belt loose or defective Check
Compressor valves defective See Table 1-3
Refrigeration system Abnormal pressures 3.3.4
No or restricted evaporator air flow 3.3.7
Expansion valve malfunction 3.3.8
Restricted refrigerant flow 4.11
Low refrigerant charge 4.8
Service valves partially closed Open
Safety device open 1.8
Liquid solenoid valve stuck closed Check
Restricted air flow No evaporator air flow or restriction 3.3.7
Heating system Reheat coolant valve stuck open 3.3.9
3.3.4 Abnormal Pressures
High discharge pressure Discharge transducer failure Replace
Refrigerant overcharge 4.8.1
Noncondensable in system Check
Condenser motor failure Check
Condenser coil dirty Clean
Low discharge pressure Discharge transducer failure 4.18
Compressor valve(s) worn or broken See Table 1-3
High suction pressure Compressor valve(s) worn or broken See Table 1-3
Low suction pressure Suction service valve partially closed Open
Filter-drier inlet valve partially closed Check/Open
Filter-drier partially plugged 4.11
Expansion valve malfunction 3.3.8
Restricted air flow 3.3.7
Suction transducer failure Replace
Suction and discharge pressures tend Compressor valve defective See Table 1-3
to equalize when system is operating
3.3.5 Abnormal Noise Or Vibrations
Compressor Loose mounting hardware Check/Tighten
Worn bearings See Table 1-3
Worn or broken valves SeeTable 1-3
Liquid slugging 3.3.8
Insufficient oil 4.15.4
Clutch loose, rubbing or is defective Check
V-belt cracked, worn or loose Check/Adjust
Dirt or debris on fan blades Clean

Table 3-3 General System Troubleshooting Procedures - Continued
INDICATION/ REFERENCE
TROUBLE POSSIBLE CAUSES SECTION
3.3.5 Abnormal Noise Or Vibrations - Continued
Condenser or evaporator fans Loose mounting hardware Check/Tighten
Defective bearings Replace
Blade interference Check
Blade missing or broken Check/Replace
3.3.6 Control System Malfunction
Will not control Sensor or transducer defective 4.16 or 4.17
Relay(s) defective Check
Microprocessor controller malfunction Check
Logic Board J3 connector unplugged
3.3.7 No Evaporator Air Flow Or Restricted Air Flow
Air flow through coil blocked Coil frosted over Defrost coil
Dirty coil Clean
Dirty filter Clean/Replace
No or partial evaporator air flow Motor(s) defective Repair/Replace
Motor brushes defective Replace
Evaporator fan loose or defective Repair/Replace
Fan damaged Repair/Replace
Return air filter dirty Clean/Replace
Icing of coil Clean/Defrost
Fan relay(s) defective Check/Replace
Safety device open 1.8
Fan rotation incorrect Check
3.3.8 Expansion Valve Malfunction
Low suction pressure with high super Low refrigerant charge 4.8
heat Wax, oil or dirt plugging valve orifice Check
Ice formation at valve seat 4.6
Power assembly failure Replace
Loss of bulb charge Replace
Broken capillary tube 4.13
Low superheat and liquid slugging in Bulb is loose or not installed. 4.13
the compressor Superheat setting too low 4.13
Ice or other foreign material holding valve open
Side to side temperature difference Wax, oil or dirt plugging valve orifice Check
(Warm Coil) Ice formation at valve seat 4.7
Power assembly failure Replace
Loss of bulb charge Replace
Broken capillary 4.13
3.3.9 Heating Malfunction
Insufficient heating Dirty or plugged heater core Clean
Reheat coolant solenoid valve(s) malfunctioning or Check/Replace
plugged Check
Low coolant level Clean
Strainer(s) plugged Open
Hand valve(s) closed Repair/Replace
Water pumps defective Repair/Replace
Auxiliary Heater malfunctioning.
No Heating Reheat coolant solenoid valve(s) malfunctioning or Check/Replace
plugged Replace
Controller malfunction Repair/Replace
Pump(s) malfunctioning 1.8
Safety device open
Continuous Heating Reheat coolant solenoid valve stuck open Replace

SECTION 4
SERVICE
WARNING
Be sure to observe warnings listed in the safety summary in the front of this manual before
performing maintenance on the hvac system.
WARNING
Read the entire procedure before beginning work. Park the coach on a level surface, with
parking brake applied. Turn main electrical disconnect switch to the off position.
NOTE
Following completion of all maintenance or service activities, the alarm queue should be cleared of any
original alarms and any alarms generated during service. Refer to paragraph 3.2.1
NOTE
To avoid damage to the earth's ozone layer, use a refrigerant recovery system whenever removing refrig
erant. When working with refrigerants you must comply with all local government environmental laws.
4.1 MAINTENANCE SCHEDULE
SYSTEM REFERENCE
SYSTEM
ON OFF SECTION
a. Daily Maintenance
X Pre-trip Inspection - after starting 2.2
X Check tension and condition of V-belt None
b. Weekly Inspection
X Perform daily inspection See above
X Check condenser, evaporator coils and air filters for cleanliness Figure 1-5
X Check refrigerant hoses and compressor shaft seal for leaks 4.6
X Feel filter-drier for excessive temperature drop across drier 4.11
c. Monthly Inspection and Maintenance
X Perform weekly inspection and maintenance See above
X Clean evaporator drain pans and hoses None
X Check wire harnesses for chafing and loose terminals Replace/Tighten
X Check fan motor bearings None
X Check compressor mounting bolts for tightness None
X Check fan motor brushes None
© 2012 Mobile Climate Control 4-1 T-348 Rev. 07/2012

4.2 OPENING TOP COVER (EVAPORATOR) b. Grasp the cover section under the bottom edge
and lift up.
To open either side of the evaporator assembly cover c. Locate metal rod (prop) secured behind the evap
do the following: (See Figure 4-1.) orator motor assemblies.
a. Twist all 5 of the 1/4 Turn cam locks counter d. Lift end of metal rod (prop) and place in plate on
clockwise. cover assembly.
1/4 Turn Cam Lock

(5 Places each side) Plate
Hinge
Figure 4-1 Opening Top Cover (Evaporator)
4.3 REMOVING TOP COVER (CONDENSER) 1/4 Turn Cam Locks

The condenser cover assembly is of one piece
construction. To remove the cover from the
condenser assembly do the following: (See
Figure 4-2.)
a. Twist all (4) of the 1/4 Turn cam locks counter
clockwise.
b. Grasp the condenser cover section under the bot
tom edge and lift up evenly.
Figure 4-2 Condenser Cover Removal

4.4 SUCTION AND DISCHARGE SERVICE VALVES 1. If the manifold gauge/hose set is new or was
exposed to the atmosphere it will need to be eva
The suction and discharge service valves (Figure 4-3) cuated to remove contaminants and air as follows:
are provided with a double seat and a gauge port, 2. Back seat (turn counterclockwise ) both field ser
which allows servicing of the compressor and vice couplers (see Figure 4-4) and midseat both
refrigerant lines. hand valves.
Turning the valve stem counterclockwise (all the way 3. Connect the yellow hose to a vacuum pump and
out) will backseat the valve to open the line to the an R-134a cylinder.
compressor and close off the gauge port. In normal
operation, the valve is backseated to allow full flow 4. Evacuate to 10 inches of vacuum and then charge
through the valve. The valve should always be with R-134a to a slightly positive pressure of 1.0
backseated before removing the gauge port cap. psig.
5. Front seat both manifold gauge set hand valves
Turning the valve stem clockwise (all the way and disconnect from cylinder. The gauge set is
forward) will frontseat the valve to isolate the now ready for use.
compressor line and open the gauge port.
b. Connecting Manifold Gauge/Hose Set
To measure suction or discharge pressure, midseat To connect the manifold gauge/hose set for reading
the valve by opening the valve clockwise 1/4 to 1/2 pressures, do the following:
turn. With the valve stem midway between
frontseated and backseated positions, the suction or 1. Remove service valve stem cap and check to make
discharge gauge port is open to both the compressor sure it is backseated. Remove access valve cap.
and the line. 2. Connect the field service coupler (see Figure 4-4)
to the access valve.
TO DISCHARGE OR VALVE STEM CAP 3. Turn the field service coupling knob clockwise,
FROM SUCTION LINE which will open the system to the gauge set.
4. Read system pressures.
5. Repeat the procedure to connect the other side of
the gauge set.
c. Removing the Manifold Gauge Set
PORT TO SERVICE VALVE 1. While the compressor is still ON, backseat the
COMPRESSOR PORT (R--22) STEM high side service valve.
Service Valve Service Valve 2. Midseat both hand valves on the manifold gauge
Frontseated Backseated set and allow the pressure in the manifold gauge
(clockwise) (counterclockwise) set to be drawn down to low side pressure. This
ACCESS VALVE returns any liquid that may be in the high side hose
(R--134a) ACCESS VALVE CAP to the system.
CAUTION
Figure 4-3 Suction or Discharge Service Valve
To prevent trapping liquid refrigerant in
4.4.1 Installing R-134a Manifold Guage Set
the manifold gauge set be sure set is
A R-134a manifold gauge/hose set with self-sealing brought to suction pressure before dis
hoses is required for service of models covered connecting.
within this manual. The manifold gauge/hose set is
available from Mobile Climate Control Transicold. 3. Backseat the low side service valve. Backseat both
(Mobile Climate Control P/N 07-00294-00, which field service couplers and frontseat both manifold
includes items 1 through 6, Figure 4-4). To perform set hand valves. Remove the couplers from the
service using the manifold gauge/hose set, do the access valves.
following:
4. Install both service valve stem caps and access
a. Preparing Manifold Gauge/Hose Set For Use valve caps (finger-tight only).

Low Pressure 1 High Pressure c. Start the system and run in cooling. Stop the unit
Gauge Gauge when suction reaches 2 psig (0.14 Bar).
d. Frontseat the compressor suction service valve (6)
to trap refrigerant in the high side of the system be
tween the compressor suction service valve and
the charge isolation valve. Wait 5 minutes to verify
that system remains at approximately 2 psig (0.14
Opened Closed Bar). If system pressure rises above 2 psig (0.14
(Backseated ) (Frontseated) Bar), open the compressor suction service valve
Hand Valve Hand Valve and repeat steps c and d until the system remains at
2 psig (0.14 Bar).
To Low Side 2 To High Side
Access Valve Access Valve e. Service or replace necessary components.
f. Leak check connections and replace filter-drier
3 (15). Refer to paragraph 4.11.
BLUE 3
RED g. Energize the Liquid Line Solenoid Valve (LSV)
(13) using an external power source (24 VDC).
h. Move the suction service hose (blue) from the
3 compressor suction service valve to the filter drier
4 2 YELLOW 4
outlet valve (16). Mid-seat the Filter Drier Outlet
6 5 Valve and evacuate the low side of the system to
(Blue Knob) (Red Knob) 500 microns. Close off the pump valve (23) and
1. Manifold Gauge Set vacuum gauge valve (22) and shut the vacuum
2. Hose Fitting (0.5-16 Acme) pump off. Wait 5 minutes to verify that vacuum
3. Refrigeration and/or Evacuation Hose holds.
. (SAE J2196/R-134a)
4. Hose Fitting w/O-ring (M14 x 1.5) i. Back-seat the filter drier outlet valve. Re-attach the
5. High Side Field Service Coupler suction service hose (blue) to the compressor suc
6. Low Side Field Service Coupler tion service valve. Open the suction service valve
Figure 4-4 Manifold Gauge Set (R-134a) (6) and charge isolation valve (11).
4.5 PUMPING THE SYSTEM DOWN OR REMOVING THE j. Disconnect external 24 VDC to liquid solenoid
REFRIGERANT CHARGE valve (13).
NOTE k. Run and check refrigerant level. Refer to para
To avoid damage to the earth's ozone layer, graph 4.8.1.
use a refrigerant recovery system whenever
removing refrigerant.
4.5.1 System Pump Down For Low Side Repair
To service or replace the filter-drier, thermostatic
expansion valve, suction line, liquid line solenoid
valve or evaporator coil, pump the refrigerant to the
condenser and receiver as follows:
a. Install manifold gauge set to compressor discharge
& suction service ports (items 2 & 6). Refer to
Figure 4-6.
b. Frontseat the charge isolation valve (11) by turning
clockwise. Disconnect suction pressure transduc
er (7), install a jumper on the compressor mounted
low pressure switch (8).

4.5.2 Refrigerant Removal From An Inoperative Com- d. Using refrigerant hoses designed for vacuum ser
pressor. vice, connect a vacuum pump to center connec
To remove the refrigerant from a compressor that is tion of manifold gauge set. Evacuate compressor
not operational, do the following: to 500 microns. Close off vacuum pump isolation
valve (15) and vacuum gauge isolation valve (14),
a. Attach a manifold gauge set as shown in Figure 4-5 and stop pump. Wait 5 minutes to verify that vacu
and isolate the compressor by front seating the dis um holds.
charge and suction service valves (items 1 & 6).
b. Recover refrigerant with a refrigerant reclaimer. If e. Once vacuum is maintained, backseat compressor
the discharge service valve port is not accessible, it service valves and disconnect manifold gauge set.
will be necessary to recover refrigerant through
the suction service valve port only. f. Check refrigerant level. Refer to paragraph 4.8.1. It
c. Service or replace components as required and may be necessary to clear any alarms that have
leak check the compressor. been generated.
Legend
Discharge
Suction 9
15
S D
4
3 2
5
14
13 10
8
6 7
12 1
11 COMPRESSOR
1. Discharge Service Valve 9. Manifold Gauge Set

2. Service Port, Discharge 10. Vacuum Pump
3. Discharge Pressure Transducer 11. Reclaimer
4. Discharge Check Valve 12. Refrigerant Cylinder
5. High Pressure Switch 13. Thermistor Vacuum Gauge
6. Service Port, Suction Service Valve 14. Vacuum Gauge Isolation Valve
7. Suction Pressure Transducer 15. Vacuum Pump Isolation Valve
8. Low Pressure Switch
Figure 4-5 Compressor Service Connections

CONDENSER
Legend
Discharge
Liquid
Suction
Refrigerant Flow 11
20
23
EVAPORATOR
22
21 18 13
15
20 19
16
14
12
17
S D
4 2 3
5
8 6
10 7
1 9
COMPRESSOR
1. Discharge Service Valve 13. Liquid Line Solenoid Valve

2. Service Port, Discharge 14. Liquid Line Sightglass
3. Discharge Pressure Transducer 15. Filter Drier
4. Discharge Check Valve 16. Filter Drier Outlet Service (King) Valve
5. High Pressure Switch 17. Manifold Gauge Set
6. Service Port, Suction Service Valve 18. Vacuum Pump
7. Suction Pressure Transducer 19. Reclaimer
8. Low Pressure Switch (to crankcase) 20. Refrigerant Cylinder
9. Dash Air Liquid Tee (Optional 21. Thermistor Vacuum Gauge
10. Dash Air Suction Tee (Optional) 22. Vacuum Gauge Isolation Valve
11. Charge Isolation Valve 23. Vacuum Pump Isolation Valve
12. Thermal Expansion Valve
Figure 4-6 Service Connections

4.5.3 Pump Down An Operable Compressor For Repair b. Connect a reclaimer to the center manifold gauge
To service an operable compressor, pump the set connection.
refrigerant into the condenser coil and receiver as c. Energize the Liquid Line Solenoid Valve (LSV)
follows: (13) using an external power source (24 VDC).
a. Install manifold gauge set. Refer to Figure 4-6. d. Recover refrigerant in accordance with reclaimer
b. Frontseat the compressor suction service valve (6) manufacturers instructions.
by turning clockwise.
c. Install a jumper on the compressor mounted low
pressure switch. Start the unit and run in cooling 4.6 REFRIGERANT LEAK CHECK
until 10 ”/hg (25.4 cm/hg) of vacuum is reached. A refrigerant leak check should always be performed
Shut the system down and tag out system power after the system has been opened to replace or repair
source. a component. To check for leaks in the refrigeration
d. Frontseat the compressor discharge service valve system, perform the following procedure:
(1) and wait 5 minutes to verify that vacuum is
maintained. If the pressure rises above vacuum, NOTE
open the compressor discharge service valve and It is emphasized that only the correct refrig
repeat steps c and d until a vacuum is maintained. erant should be used to pressurize the sys
e. Service or replace components as required and tem. Use of any other refrigerant will con
leak check the compressor. taminate the system, and require additional
NOTE evacuation.
To avoid the entrance of air, never evacuate a. Ensure the service valves are open and power the
an open drive compressor below 500 mi liquid line solenoid valve from an external source.
crons. b. If system is without refrigerant, charge system
with refrigerant vapor to build up pressure to
f. Using refrigerant hoses designed for vacuum ser approximately 30 PSIG (R-134a).
vice, connect a vacuum pump to the center con
nection of the manifold gauge set. Evacuate com c. Add sufficient nitrogen to raise system pressure to
pressor to 500 microns. Close off pump valve (23), 150 to 200 psig (10.21 to 13.61 bar).
isolate vacuum gauge valve (22) and stop pump. d. Check for leaks. The recommended procedure for
Wait 5 minutes to verify that vacuum holds. finding leaks in a system is with an electronic leak
g. Once vacuum is maintained, re-connect low pres detector. Testing joints with soap suds is satisfac
sure switch. Backseat compressor service valves tory and may be necessary under conditions when
and disconnect manifold gauge set. an electronic leak detector will not function cor
rectly.
h. Check refrigerant level. Refer to paragraph 4.8.1. It
may be necessary to clear any alarms that have e. Remove test gas and replace filter-drier.
been generated. f. Evacuate and dehydrate the system. Refer to para
4.5.4. Removing Entire System Charge graph 4.7.
To remove the entire refrigerant charge, do the g. Charge the unit. Refer to paragraph 4.8.
following: h. Ensure that a Logic Board self-test has been per
a. Connect a manifold gauge set to the system as formed and that there are no errors or alarms indi
shown in Figure 4-6. cated. (Refer to paragraph 2.1.3.)

4.7 EVACUATION AND DEHYDRATION g. Remove external 24 VDC from Liquid Line Sole
noid.
4.7.1 General
h. Charge system. Refer to paragraph 4.8.2.
The presence of moisture in a refrigeration system
can have many undesirable effects. The most 4.7.4 Procedure for Evacuation and Dehydrating Sys-
common are copper plating, acid sludge formation, tem (Triple Evacuation)
“freezing-up” of metering devices by free water, and a. Remove refrigerant using a refrigerant recovery
formation of acids, resulting in metal corrosion. A system. Refer to paragraph 4.5.4.
triple evacuation (Refer to paragraph 4.7.4) should
be performed after a major system repair b. The recommended method is connecting lines (re
(compressor, evaporator, or condenser frigerant hoses designed for vacuum service) as
replacement). A one time evacuation (Refer to shown in Figure 4-6.
paragraph 4.7.3) should take place after a minor c. Energize the Liquid Line Solenoid Valve (LSV)
system repair (replacement of a solenoid valve or a (13) using an external power source (24 VDC).
filter drier).
d. Start vacuum pump. Slowly open valves halfway
4.7.2 Preparation and then open vacuum gauge valve.
NOTE e. Evacuate unit until vacuum gauge indicates 2000
Using a compound gauge for determination microns Hg vacuum. Close gauge valve, vacuum
of vacuum level is not recommended be pump valve, and stop vacuum pump.
cause of its inherent inaccuracy. f. Break the vacuum with nitrogen. Raise system
pressure to approximately 2 psig.
a. Evacuate and dehydrate only after pressure leak g. Purge the nitrogen from the system.
test. Refer to paragraph 4.6.
h. Repeat steps d. thru g. one time.
b. Essential tools to properly evacuate and dehydrate
any system include a good vacuum pump with a i. Start vacuum pump and open all valves. Dehy
minimum of 6 cfm (10.2 m3/hr) volume displace drate unit to 500 microns Hg vacuum.
ment, (MCC P/N 07-00176-11), and a good vacu j. Close off pump valve (23), and stop pump. Wait
um indicator (MCC P/N 07-00414-00). five minutes to see if vacuum holds.
c. Keep the ambient temperature above 60°F k. Remove external 24 VDC from Liquid Line Sole
(15.6°C) to speed evaporation of moisture. If am noid.
bient temperature is lower than 60°F (15.6°C), ice
may form before moisture removal is complete. l. Charge system. Refer to paragraph 4.8.2.
4.7.3 Procedure for Evacuation and Dehydrating Sys- 4.8 ADDING REFRIGERANT TO SYSTEM
tem (One Time Evacuation)
a. Remove refrigerant using a refrigerant recovery 4.8.1 Checking Refrigerant Charge
system. Refer to paragraph 4.5.4. The following conditions must be met to accurately
b. The recommended method is connecting lines (re check the refrigerant charge.
frigerant hoses designed for vacuum service) as a. Coach engine operating at high idle.
shown in Figure 4-6.
b. Unit operating fully loaded (six cylinder) in cool
c. Energize the Liquid Line Solenoid Valve (LSV) mode for 15 minutes.
(13) using an external power source (24 VDC).
c. Compressor discharge (head) pressure to 150
d. Start vacuum pump. Slowly open valves halfway PSIG (R-134a). It may be necessary to block con
and then open vacuum gauge valve (items 22 & denser air flow to raise discharge pressure.
23).
d. Under the above conditions, the system is proper
e. Evacuate unit until vacuum gauge indicates 500 ly charged when the white balls are floating and a
microns Hg vacuum. liquid level is detected in the receiver sight glasses.
f. Close off pump valve (23), and stop pump. Wait Adjust the charge (add or remove) to meet this
five minutes to see if vacuum holds. condition.

4.8.2 Adding Full Charge vapor charge until the white balls are floating and a
liquid level is detected in the receiver sight glasses.
a. Install manifold gauge set at the compressor suc
tion and discharge service valve ports. See figure d. Backseat the suction service valve. Close the vapor
Figure 4-6. valve on the refrigerant drum and note weight. Re
move the manifold gauge set and replace all valve
b. Evacuate and dehydrate system. Refer to para caps.
graph 4.7.
4.9 CHECKING FOR NONCONDENSIBLES
NOTE
To check for noncondensibles, proceed as follows:
Evacuation can be performed at the com
pressor but liquid charging should only be a. Stabilize system to equalize pressure between the
suction and discharge side of the system.
done at the charge isolation valve on the bus
roof (See Figure 4-6, Item 11) or the dis b. Check temperature at the condenser and receiver.
charge line service port (See Figure 4-6, Item c. Check pressure at the filter-drier inlet service
2). valve.
d. Check saturation pressure as it corresponds to the
c. Place appropriate refrigerant cylinder on scales. condenser/receiver temperature using the Tem
Prepare to charge liquid refrigerant into the system perature-Pressure Chart, Table 4-4.
by connecting the charging hose from refrigerant e. If gauge reading is 3 psig (0.20 bar) or more than the
cylinder (20) to the charge isloation valve(11). saturation pressure in step d, noncondensibles are
d. Energize the Liquid Line Solenoid Valve (LLSV) present.
(13) using an external power source (24 VDC). f. Remove refrigerant using a refrigerant recovery
system.
e. Note weight of refrigerant and cylinder.
g. Evacuate and dehydrate the system. Refer to para
f. Open cylinder valve (20) and purge hose at charge graph 4.7.4.
isolation valve (11).
h. Charge the unit. Refer to paragraph 4.8.2.
g. Midseat filter drier inlet valve to allow liquid refrig
erant to flow into the low side. 4.10 CHECKING AND REPLACING HIGH OR LOW PRES-
h. When correct charge has been added, refer to SURE SWITCH
paragraph 1.5, close cylinder valve.
i. Remove 24 VDC from Liquid Line Solenoid . WARNING
j. Backseat charge isolation valve. Do not use a nitrogen cylinder without a
k. Check charge level in accordance with the proce pressure regulator
dures of paragraph 4.8.1.
4.8.3 Adding Partial Charge
a. Install manifold gauge set at the compressor suc
WARNING
tion service valve. See Figure 4-6. Do not use oxygen in or near a refrigera
b. Place appropriate refrigerant cylinder on scale. tion system as an explosion may occur.
Prepare to charge vapor refrigerant by connecting
charging hose from container to center connec a. Disconnect wiring and remove switch from unit.
tion on gauge manifold. Purge air from hoses. All units are equipped with a schrader valve at the
pressure switch connections.
c. Run the unit in the cool mode as described in sec
tion 4.8.1. With the suction service valve mid b. Connect switch to a cylinder of dry nitrogen. See
seated, open the refrigerant cylinder valve and add Figure 4-7.

1 2
4 1
2 5
6 3 4 3 5
1. Filter--Drier Inlet Solenoid Valve
3 2. Valve Service Port
3. Hex Nut (ORS)
4. Filter--Drier
5. Filter--Drier Outlet Service Valve
Figure 4-8 Filter-Drier Removal
1. Cylinder Valve and Gauge
2. Pressure Regulator 4.11.2 To Replace Filter-Drier
3. Nitrogen Cylinder
4. Pressure Gauge (0 to 400 psig = 0 to a. Perform a low side pump down. Refer to para
27.22 bar) graph 4.5.1, (steps a. to c.)
5. Bleed-Off Valve
6. 1/4 inch Connection b. Turn the driver's A/C switch to “OFF” position.
c. Frontseat the filter-drier outlet service valve and
place a new filter-drier near the unit for immediate
Figure 4-7 Checking High Pressure Switch installation.
c. Connect an ohmmeter across switch terminals. d. Remove the filter-drier clamp.
d. Set nitrogen pressure regulator higher than the up
per switch setting. (refer to paragraph 1.5.) WARNING
e. For a high pressure switch, close cylinder valve and
open bleed-off valve. Open cylinder valve and The filter-drier may contain liquid refrig
slowly close bleed-off valve. The switch should erant. Slowly loosen the ORS hex nuts to
open, (no continuity) within required cut out tol avoid refrigerant contact with exposed
erance. Close cylinder valve and release pressure skin or eyes.
through the bleed-off valve. As pressure drops,
switch should close, (continuity) within required e. Using two open end wrenches, slowly crack open
cut in tolerance. the ORS hex nuts on each side of the filter-drier.
f. For a low pressure switch, close cylinder valve and Remove the filter-drier.
bleed-off valve. Open cylinder valve to bring pres f. Remove seal caps from the new filter-drier. Apply
sure above the cutout setting. Close the cylinder a light coat of compressor oil to the O-Rings and
valve and slowly open bleed-off valve. The switch seat in the grooves of the filter-drier.
should open, (no continuity) within required cut g. Assemble the new filter-drier to lines ensuring that
out tolerance. Open cylinder valve and increase the arrow on the body of the filter-drier points in
pressure by closing the bleed-off valve. As pres the direction of the refrigerant flow (refrigerant
sure increases, switch should close, (continuity) flows from the receiver to the evaporator), and
within required cut in tolerance. that the O-Rings have remained in place. Finger
g. Replace or re-install switch and reconnect wiring. tighten ORS hex nuts.
h. Tighten the filter-drier ORS hex nuts using two
4.11 FILTER-DRIER open end wrenches.
i. Evacuate the filter-drier and lines by connecting a
4.11.1 To Check Filter-Drier vacuum pump as shown in Figure 4-6. Evacuate to
The filter-drier (see Figure 4-8) must be changed if 500 microns.
the drier is partially restricted or service has been j. Backseat (fully close) the service valve port and re
performed on the refrigerant system. Check for a place valve cap.
restriction by feeling the inlet and outlet lines of the
filter-drier. If the outlet side feels cooler than the k. Test filter-drier for leaks.
inlet side, then the filter-drier should be changed l. Check refrigerant level.

4.12 SERVICING THE LIQUID LINE SOLENOID VALVE b. Carefully loosen enclosing tube assembly and en
sure no pressure remains within the valve. Disas
The Liquid line solenoid valve (Figure 4-9) requires semble valve and replace defective parts.
no maintenance unless a malfunction to the internal
parts or coil occurs. This may be caused by foreign c. Assemble valve and leak check.
material such as: dirt, scale, or sludge in the
refrigeration system, or improper voltage to the coil. d. Evacuate low side and re-open system.
There are only three possible valve malfunctions: coil 4.12.3 Replace Entire Valve
burnout, failure to open, or failure to close. a. Perform a low side pump down. Refer to para
Coil burnout may be caused by the following: graph 4.5.1.
1 Improper voltage. b. Remove coil assembly. Refer to paragraph 4.12.1.
2 Continuous over-voltage, more than 10% or un c. Disconnect valve from liquid line and filter-drier.
der-voltage of more than 15%.
d. Unbolt valve body from frame and remove from
3 Incomplete magnet circuit due to the omission of unit. See Figure 4-9, item 8.
the coil housing or plunger.
e. Install new valve onto frame.
4 Mechanical interface with movement of plunger
which may be caused by a deformed enclosing f. Apply a light coat of oil to the O-Rings and con
tube. nect the liquid line and the filter-drier.
Failure to open may be caused by the following: g. Leak check connections.
1 Coil burned out or an open circuit to coil connec h. Evacuate low side and re-open charge isolation
tions. valve.
2 Improper voltage.
i. Replace coil assembly and test operation.
3 Defective plunger or deformed valve body assem
bly.
1
Failure to close may be caused by the following:
2
1 Defective plunger or deformed valve body assem 3
bly.
2 Foreign material in the valve. 4
4.12.1 Coil Replacement
5
a. It is not necessary to remove the refrigerant charge
from the system. 6
b. Place main battery disconnect switch in OFF posi 7
tion and lock.
c. Disconnect wire leads to coil.
d. Remove coil locking nut and O-Ring, then the
threaded collar.
e. Lift coil from enclosing tube and replace. 8
f. With the coil installed replace the threaded collar,
then the O-Ring and locking nut. 1. Locking Nut 5. Plunger Assembly
2. O--Ring 6. O-Ring
g. Connect wire leads and test operation 3. Threaded Collar 7. Body
8. Mount
4.12.2 Internal Part Replacement 4. Coil
a. Perform a low side pump down. Refer to para
graph 4.5.1 . Figure 4-9 Liquid Line Solenoid Valve

4.13 THERMOSTATIC EXPANSION VALVE g. Reinstall the valve assembly into the unit, again
taking care to oil and install new O-Rings.
The thermostatic expansion valve (Figure 4-9) is an
automatic device which maintains constant h. Fasten equalizer line to the expansion valve.
superheat of the refrigerant gas leaving the i. Leak check the new valve and evacuate and dehy
evaporator regardless of suction pressure. The valve drate low side. Refer to paragraph 4.5.1.
functions are: (a) automatic control of refrigerant j. The thermal bulb is installed below the center of
flow to match the evaporator load and (b) the suction line (four or eight o'clock position).
prevention of liquid refrigerant entering the This area must be clean to ensure positive bulb
compressor. Unless the valve is defective, it seldom contact. Strap thermal bulb to suction line. Ensure
requires any maintenance. that retaining straps are tight and renew insulation.
k. If required, add vapor refrigerant to bring low side
1 pressure to 20 to 30 PSIG (R-134a). Open filter-
7 drier inlet service valve and compressor service
7 valves.
5
l. Run the coach for approximately 30 minutes on
fast idle.
m.Check refrigerant level. Refer to paragraph 4.8.1.
n. Check superheat. Refer to paragraph 4.13.2.
2
4.13.2 Superheat Measurement
6 4 6
3 NOTE
All readings must be taken from the TXV
bulb location and out of the direct air stream.
1. Power Head 4. Body
Assembly 5. ORS Fitting
2. Equalizer Connection 6. O--Ring
3. Bulb 7. ORS Adapter Fitting
3
4
2
Figure 4-10 Thermostatic Expansion Valve 5
1
4.13.1 Valve Replacement 1. Suction Line 4. Thermocouple

a. Pump down low side of the unit. Refer to para (section view) 5. TXV Bulb (Shown
graph 4.5.1. 2. TXV Bulb Clamp in the 4’clock
3. Nut & Bolt (clamp) position)
b. Remove insulation from expansion valve and
bulb. See Figure 4-10 and Figure 4-11. Figure 4-11 Thermostatic Expansion Valve Bulb and
Thermocouple
c. Loosen retaining straps holding bulb to suction
line and detach bulb from the suction line. a. Remove Presstite insulation from expansion valve
bulb and suction line.
d. Loosen flare nuts on equalizer line and disconnect
equalizer line from the expansion valve. b. Loosen one TXV bulb clamp and make sure area
under clamp is clean.
e. Using two open end wrenches, slowly crack open
the ORS hex nuts on each side of the valve as c. Place temperature thermocouple in contact with
sembly. Remove the valve assembly from the unit. the suction tube and parallel to the TXV bulb, and
then secure loosened clamp making sure both
f. Remove the adapter fittings from the valve and in bulb and thermocouple are firmly secured to suc
stall the fittings on the new valve using care to oil tion line. See Figure 4-11. Reinstall insulation
and install new O-Rings. around the bulb.

d. Connect an accurate low pressure gauge to the low d. Reverse procedure to install new filters and close
pressure port (Figure 1-6). the covers.
e. Start bus and run on fast idle until unit has stabi
lized, about 20 to 30 minutes. 4.15 COMPRESSOR MAINTENANCE
4.15.1 Removing the Compressor
NOTE
If compressor is inoperative and the unit still has
When conducting this test, the suction pres refrigerant pressure, isolate the compressor and
sure must be at least 6 psig (0.41 bar) below remove the refrigerant. Refer to paragraph 4.5.2. If
the expansion valve maximum operating compressor is operative, perform a pump down.
pressure (MOP). Refer to paragraph 1.5 for Refer to paragraph 4.5.3.
MOP. a. Place main battery disconnect switch in OFF posi
tion and lock.
f. From the temperature/pressure chart (Table 4-4), b. Tag and disconnect wiring to the high pressure and
determine the saturation temperature corre low pressure switch, unloaders and clutch.
sponding to the evaporator outlet pressure.
c. Remove tension on drive belts, remove drive belts.
g. Note the temperature of the suction gas at the ex
pansion valve bulb. Subtract the saturation tem d. Loosen bolts at suction and discharge service valve
perature from this temperature. The difference is flanges and break seal to be sure pressure is re
the superheat of the suction gas. leased. Remove bolts.
h. The superheat may cycle from a low to high read e. Remove four bolts holding compressor to base
ing. Monitor the superheat taking readings every f. Attach sling or other device to the compressor and
3-5 minutes for a total of 5-6 readings. Calculate remove compressor from the coach through the
the superheats, add the readings and divide by the rear access door.
number of readings taken to determine average su
perheat. Refer to paragraph 1.5 for superheat set NOTES
ting.
i. If superheat is not within tolerance, replace the 1 Service replacement compressors are
valve. sold without service valves. Valve pads
are installed in their place. The optional
4.14 REPLACING EVAPORATOR RETURN AIR FILTERS unloaders are not supplied, as the
cylinder heads are shipped with plugs.
The evaporator return air filters are located in the Customer should retain the original
evaporator section next to the evaporator coils. unloader valves for use on the
Access to the filters is accomplished by removing the replacement compressor.
evaporator covers.
The filters should be checked for cleanliness 2 The piston plug that is removed from the
periodically depending on operating conditions. A replacement compressor head must be
dirty filter will restrict air flow over the evaporator installed in the failed compressor if
coil which may cause insufficient cooling or heating returning for warranty or core credit.
and possible frost buildup on the coil. To remove the
filters, do the following. 3 Do not interchange allen-head
a. Place main battery disconnect switch in OFF posi capscrews that mount the piston plug
tion and lock. and unloader, they are not
interchangeable.
b. Open the evaporator top cover. Refer to para
graph 4.2. 4 Check oil level in service replacement
c. Grasp and lift the filter elements out using care not compressor. Refer to paragraphs 1.5 and
to damage the evaporator coil. 4.15.4.

i. Remove clutch assemble and retain original clutch
12 1 key. Install on replacement compressor.
2 j. Install compressor in unit by performing the re
11 3 moval steps in reverse. It is recommended that
new locknuts be used when replacing compressor.
4
10 Install new gaskets on service valves and tighten
9 5 bolts uniformly (55 to 80 ft-lbs suction and 20 to
30 ft-lbs discharge service valves).
8 k. Leak check connections and replace filter-drier.
6 Refer to paragraph 4.11.
7 l. Using refrigerant hoses designed for vacuum ser
vice, connect a vacuum pump (see Figure 4-6) and
evacuate compressor to 500 microns. Front seat
1. Electric Unloader 6. Bottom Plate both manifold valves to isolate the pump.
Valve 7. Oil Drain Plug m.Open compressor service valves.
2. Suction Service 8. Oil Level Sight Glass
Valve Charging Port 9. Oil Pump n. Start unit and check refrigerant level. Refer to
3. Suction Service 10. O--ring paragraph 4.8.1.
Valve 11. Discharge Service
o. Check compressor oil level. Refer to paragraph
4. Clutch Valve
4.15.4. Add or remove oil if necessary.
5. Oil Fill Plug 12. Service Port
p. Check compressor unloader operation. Refer to
paragraph 4.15.5
Figure 4-12 Compressor q. Backseat compressor service valves.
g. Remove the three socket head capscrews from the r. Remove manifold gauge set. Refer to paragraph
cylinder head(s) that have unloader valves instal 4.4.1.
led. See Figure 4-13. Remove the unloader valve
and bypass piston assembly, keeping the same 4.15.2 Transferring Compressor Clutch
capscrews with the assembly. The original un To remove a clutch (see Figure 4-14) from a
loader valve must be transferred to the replace compressor and install on a replacement
ment compressor. The plug arrangement re compressor, do the following:
moved from the replacement is installed in the
original compressor as a seal. If piston is stuck, it
may be extracted by threading a socket head 1
2
capscrew into top of piston. A small Teflon seat
ring at the bottom of the bypass piston plug must 3
be removed.
4 5
7
GASKET SPRING 6
FLANGE 8
COVER
COMPRESSOR
HEAD
CAPSCREWS
BYPASS (NOT INTERCHANGEABLE WITH
PISTON CONTROL VALVE SCREWS)
PLUG 1. Compressor 6. Armature
2. Seal Cover 7 Spacer Nuts
Figure 4-13 Removing Bypass Piston Plug 3. Coil 8. Retaining Capscrew,
4. Rotor Lockwasher, 3/8 Washer
h. Remove the pressure switches and install on re 5. Rotor Nut
placement compressor after checking switch op
eration. Refer to paragraph 4.10. Figure 4-14 Compressor Clutch

4.15.2 Transferring Compressor Clutch (Continued) Electric will have an upgraded armature plate
a. Place main battery disconnect switch in OFF posi installed. This new armature plate will eliminate the
need for separate shims. The shim pack has been
tion and lock. replaced by three adjusting screws installed on the
b. Tag and disconnect wiring to the clutch. spring plate of the armature. Armature to rotor
c. Remove tension on drive belts, remove drive belts. clearance will stay the same (.030”-.060”) but the
procedure to adjust will be different from original
d. Remove the armature as a complete assembly by shim style clutch. Clutch assemblies are
removing the retaining capscrew, lockwasher, and interchangeable. The clearance is factory set on each
special 3/8 washer from the compressor crank clutch, but should the need arise to adjust the clutch
shaft. Use special tool (MCC P/N 07-00240-01) to gap the following procedure should be followed.
prevent crankshaft rotation. Three Point Clutch Adjustment Procedure
e. Install a 7/8-14 x 4” (MCC P/N 07-00381-00) a. Confirm the clutch electrical circuit can not be en
capscrew into the center hole of the armature as ergized while you are working on clutch.
sembly and use it as a jacking bolt to remove the
armature. Use tool (MCC P/N 07-00240-01) as in
step a. to prevent crankshaft rotation. WARNING
f. Using special tool (MCC P/N 07-00242-01), re
move the rotor nut and rotor. Retain original key. Battery disconnect should be off.
g. Noting the position of the wire, remove the three b. With a .045” feeler gauge check the clearance at the
bolts holding the coil to the compressor. three set screws and determine what adjustment
h. Remove every other bolt from the seal cover of the needs to be made. Clearance is to be .045” +-
new compressor in the same manner as the origi .015”.
nal compressor. Mount the coil assembly with the c. With a 1/8” hex socket wrench and a 7/16” box
wire in the same orientation as it was mounted on wrench to hold the locking nut, back off the three
the original compressor. Tighten the mounting set screws until they do not contact the armature
bolts to 45-50 ft/lbs (5.53-6.92 mkg). plate.
i. Mount the rotor on the shaft. Seat the rotor to the d. Turn the set screws CW until they just make con
hub, using the rotor nut. Be sure pulley turns freely tact with the armature plate. Adjust clockwise one
without binding. Tighten rotor nut by first noting and one half turns after contact. One and one half
torque necessary to start the nut on the hub and turns equals approximately .040”.
then adding 50 ft/lbs of torque.
e. Measure the initial clearance after the one and one
j. Install armature on shaft using original key and half turns CW and adjust for a clearance between
tighten mounting bolt to 20 ft/lbs (2.8 mkg). .030” and .060”. All three set screw locations
k. Perform a check of the air gap between the inside should be very close in clearance dimensions.
face of the armature and the mating face of the ro f. When clearance is set lock the adjusting screws
tor. The air gap should be measured with a mini with the nuts torqued to 7 foot pounds. You will
mum of 50 psig (3.4 bar) in the crankcase. A pre need to hold the hex socket adjusting screw while
liminary check may be performed before the torquing the lock nut.
crankcase is pressurized but a final check must be
performed before the clutch is operated. The gap NOTE
should be between 0.030 and 0.060 inch (7.62 to Setting clearance is done with 50 psig in the compres
15.24 mm). If required, remove the six armature sor due to the crankshaft movement when charged. If
spacer nuts and spacer. Add or remove shims to there is not 50 psig in the compressor when the clear
adjust gap. Reinstall spacer nuts and tighten to 7-8 ance is set the clearance should be set on the lower
ft/lbs (1.0 to 1,1 mkg). end of the tolerance to allow for crankshaft move
l.Reconnect wiring and test clutch operation. ment when charged. Check clearance again after com
pressor is pressurized.
4.15.3 Shim-less Compressor Clutch
As of February 4, 2008 all 05G and 05K compressor g. Reconnect battery wiring and test clutch opera
clutches supplied by MCC and built by Warner tion.

4.15.4 Compressor Oil Level 3. Evacuate the compressor to 500 microns. Back
seat the compressor service valves and repeat the
To check, and if required correct, the compressor oil oil level check procedure.
level do the following:
f. To add oil to the compressor, do the following:
a. Operate the coach for at least one-half hour at fast
idle speed, with the temperature controls at the 1. With the system off, connect a manifold gauge set
coolest setting, and the compressor fully loaded. It to the compressor suction and discharge service
may be necessary to pre-heat the coach and/or op valves. Front seat both service valves to isolate the
erate the system in the reheat mode to keep the compressor from the system (See Figure 4-6) and
compressor fully loaded throughout this proce reclaim the refrigerant to below atmospheric
dure pressure. Shut off the reclaimer and verify the
pressure does not rise. If the pressure rises, con
b. Ensure the system is fully charged (refer to para tinue reclaiming until the pressure remains below
graph 4.8.1) and the compressor crankcase is atmospheric.
warm to the touch after fifteen minutes of opera
tion. 2. Add oil to compressor crankcase slowly, through
the oil fill plug opening (see Figure 4-12) to bring
c. Shut off the system and immediately record the oil level to mid range of allowed levels.
level in the compressor sight glass. See 3. Evacuate compressor to 500 microns. Backseat
Figure 4-12. If the compressor is not level, an aver compressor suction and discharge valves, start
age between the sight glass levels will have to be system and recheck oil level.
made to determine level.
4. Remove manifold gauge set.
d. The correct oil level for this application should be
between the bottom and 1/2 of the oil level sight 4.15.5 Checking Unloader Operation
glass. See Figure 4-12. If the oil level is correct, re To check unloader operation do the following:
lease the coach into service. If the level is above the
1/2 sightglass maximum, proceed to step e. If the a. Install a manifold gauge set as shown in Figure 4-6.
level is below the 1/2 sightglass maximum proceed Ensure both manifold valves are frontseated and
to step f. center connection is tight on blank fitting.
b. Midseat compressor suction service valve.
c. Disconnect the suction pressure transducer
WARNING Figure 1-6. This will force the controller to ener
gize the unloader(s).
Extreme care must be taken to ensure
d. Start the bus and run in cooling, lower set point if
that all the refrigerant has been removed required to ensure system remains in full speed
from the compressor crankcase or the re cooling.
sultant pressure will forcibly discharge e. Locate the unloader connector at the compressor.
compressor oil. Observe manifold suction gauge while unplugging
the connector. Pressure should decrease 3 to 5 psi
e. To remove oil and bring the level to the 1/2 sight (0.2 to 0.4 bar) when the unloader is unplugged
glass maximum, do the following: and increase the same amount as the plug is recon
nected. Repeat test for second unloader if fitted.
1. With the system off, connect a manifold gauge set
to the compressor suction and discharge service f. If pressures do not react as described, check un
valves. Front seat the service valves to isolate the loader coil or repair unloader mechanism as re
compressor from the system (See Figure 4-6) and quired.
reclaim the refrigerant to below atmospheric g. When testing is complete, reconnect transducer
pressure. Shut off the reclaimer and verify the and unloader connectors and remove manifold
pressure does not rise. If the pressure rises, con gauge set.
tinue reclaiming until the pressure remains below
atmospheric. h. Disconnection of the suction pressure transducer
will cause an “A15” alarm. Once the transducer is
2. Drain or pump out compressor oil until the level reconnected, the alarm will go to inactive and can
is brought to the proper level. then be cleared.

4.16 TEMPERATURE SENSOR CHECKOUT a. With the system running use the driver display and
manifold gauges to check suction and/or dis
a. An accurate ohmmeter must be used to check re charge pressure(s) simultaneously.
sistance values shown in Table 4-1.
b. Determine with the gauges whether one or both
b. Due to variations and inaccuracies in ohmmeters, pressure readouts are correct. If one is correct, ex
thermometers or other test equipment, a reading change the pressure transducer locations. If the
within two percent of the chart value would be problem moves with the transducer, replace the
considered acceptable. If a sensor is bad, the resist faulty transducer.
ance value would usually be much higher or lower
than the value given in Table 4-1. c. If the driver display read out disagrees with both
values shown on the manifold gauges proceed to
c. At least one sensor lead must be disconnected step d.
from the controller before any reading can be tak
en. Not doing so will result in a false reading. Two
preferred methods of determining the actual test CAUTION
temperature at the sensor are an ice bath at 32°F
(0°C) and/or a calibrated digital temperature me Use care when checking/manipulating
ter. wires/plugs attached to the Logic Board.
Table 4-1 Temperature Sensor Resistance Damage to the board or wiring harness
can occur.
Temperature
Resistance In Ohms d. Verify that the wiring to the transducer(s) is in
°F °C
good condition.
-20 -28.9 165,300
-10 -23.3 117,800 e. Use a digital volt-ohmmeter to measure voltage
across the transducer connector corresponding to
0 -17.8 85,500
terminals A & B. See Figure 4-15. The reading
10 -12.2 62,400 should be 5.0 VDC.
20 - 6.7 46,300
f. Use a digital volt-ohmmeter to measure wire conti
30 - 1.1 34,500 nuity between the connector positions corre
32 0 32,700 sponding to: C (See Figure 4-15) and J6-23 (suc
40 4.4 26,200 tion) (Logic Board) or C (See Figure 4-15) and
50 10.0 19,900 J6-20 (discharge) (Logic Board). See Figure 5-2 for
Logic Board locations.
60 15.6 15,300
70 21.1 11,900 g. Use a digital volt-ohmmeter to measure voltage
across the transducer at terminals A & C. See
77 25 10,000
Figure 4-15. Compare to values in Table 4-1. A
80 26.7 9,300 reading within two percent of the values in the
90 32.2 7,300 table would be considered good.
100 37.8 5,800
110 43.3 4,700
120 48.9 3,800 C
A B
4.17 PRESSURE TRANSDUCER CHECKOUT
NOTE
System must be operating to check transduc
ers. Figure 4-15 Transducer Terminal Location

4.18 REPLACING SENSORS AND TRANSDUCERS er. Sensor/transducer connections are fitted with
Schreader valves to facilitate replacement.
a. Place main battery disconnect switch in OFF posi d. Connect wiring to replacement sensor or trans
tion and lock. ducer.
b. Tag and disconnect wiring from defective sensor e. Checkout replacement sensor or transducer. Refer
or transducer. to section 4.16 or 4.17 as applicable.
f. Repair or replace any defective component(s), as
c. Remove and replace defective sensor or transduc required.
Table 4-2 Pressure Transducer Voltage

“/hg Voltage Psig Voltage Psig Voltage Psig Voltage Psig Voltage Psig Voltage
20” 0.369 40 0.858 95 1.397 150 1.936 205 2.475 260 3.014
10” 0.417 45 0.907 100 1.446 155 1.985 210 2.524 265 3.063
Psig Voltage 50 0.956 105 1.495 160 2.034 215 2.573 270 3.112
0 0.466 55 1.007 110 1.544 165 2.083 220 2.622 275 3.161
5 0.515 60 1.054 115 1.593 170 2.132 225 2.671 280 3.210
10 0.564 65 1.103 120 1.642 175 2.181 230 2.720 285 3.259
15 0.614 70 1.152 125 1.691 180 2.230 235 2.769 290 3.308
20 0.663 75 1.204 130 1.740 185 2.279 240 2.818 295 3.357
25 0.712 80 1.250 135 1.789 190 2.328 245 2.867 300 2.406
30 0.761 85 1.299 140 1.838 195 2.377 250 2.916 305 3.455
35 0.810 90 1.348 145 1.887 200 2.426 255 2.965 310 3.504

4.19 LOGIC BOARD REPLACEMENT
Control configuration is preset by the manufacturer and resetting of the parameters is not advised. If a
replacement Logic Board is installed, it is necessary to match the configuration jumpers (See Figure 1-10) to the
original board. Table 4-3 provides a list of jumper functions. MCC is not responsible for failures or damage
resulting from unauthorized changes.
Table 4-3 Logic Board Configuration
Configuration Description
High Reheat - When this configuration is removed, the unit will default to high speed in reheat mode and
A in the low speed cool band. If not removed, heat/reheat will default to low speed.
High Vent - When this configuration is removed, the unit will default to high speed in vent mode. If not
B* removed vent mode will default to low speed.
C* Dry Heat - When this configuration is removed, the unit will run on 100% reheat instead of heat.
Reheat/Cycle - When the reheat cycle configuration is removed, the unit is in reheat mode. The default
D configuration is cycle clutch mode.
E Transducers - When the transducer configuration is removed, transducers will assume to be present.
Refrigerant R-22/R-134a - When the refrigerant configuration is removed, the refrigerant is set for R-22.
F* The default refrigerant is R-134a.
G Unit Type - Rearmount unit enabled with “G” removed and “H” installed.
H Unit Type - With “H” removed and “G” installed, roof top unit will be enabled.
I Factory - Reserved for the manufacturer.
Invert H2O - When this configuration is removed, the logic for the water temperature switch will be in
J* verted.
K Voltage - When this configuration is removed, the voltage selection will be changed from 12 to 24 vdc.
L Factory - Reserved for the manufacturer.
Psig/Bars - When this configuration is removed, the display will indicate pressures in bars. When not re
M* moved, the display will indicate pressures in psig.
°C/°F - When this configuration is removed, the display will show temperatures in °F. When not removed
N the display will show temperatures in °C.
PI Reheat - When this configuration is removed, reheat mode will use the PI algorithm to vary the duty
O* cycle of the heat valve. If it is not removed, the heat valve will be on constantly.
Low Ambient Lockout - When this configuration is removed, the compressor clutch will disengage at 25°F.
P* With this configuration in place, the compressor will disengage at 45°F.
NOTE: * Designates N.J.T. Jumpers

Table 4-4 R-134a Temperature - Pressure Chart
Temperature Vacuum Temperature Pressure

°F °C “/hg Kg/cm@ Bar °F °C Psig Kg/cm@ Bar
-40 -40 14.6 37.08 0.49 28 -2 24.5 1.72 1.69
.35 .37 12.3 31.25 0.42 30 -1 26.1 1.84 1.80
-30 -34 9.7 24.64 0.33 32 0 27.8 1.95 1.92
-25 -32 6.7 17.00 0.23 34 1 29.6 2.08 2.04
-20 -29 3.5 8.89 0.12 36 2 31.3 2.20 2.16
-18 -28 2.1 5.33 0.07 38 3 33.2 2.33 2.29

40 4 35.1 2.47 2.42
-16 -27 0.6 1.52 0.02
45 7 40.1 2.82 2.76
Temperature Pressure 50 10 45.5 3.20 3.14
°F °C Psig Kg/cm@ Bar 55 13 51.2 3.60 3.53
-14 -26 0.4 0.03 0.03 60 16 57.4 4.04 3.96
-12 -24 1.2 0.08 0.08 65 18 64.1 4.51 4.42
-10 -23 2.0 0.14 0.14 70 21 71.1 5.00 4.90
-8 -22 2.9 0.20 0.20 75 24 78.7 5.53 5.43
-6 -21 3.7 0.26 0.26 80 27 86.7 6.10 5.98
-4 -20 4.6 0.32 0.32 85 29 95.3 6.70 6.57
-2 -19 5.6 0.39 0.39 90 32 104.3 7.33 7.19
0 -18 6.5 0.46 0.45 95 35 114.0 8.01 7.86
2 -17 7.6 0.53 0.52 100 38 124.2 8.73 8.56
4 -16 8.6 0.60 0.59 105 41 135.0 9.49 9.31
6 -14 9.7 0.68 0.67 110 43 146.4 10.29 10.09
8 -13 10.8 0.76 0.74 115 46 158.4 11.14 10.92
10 -12 12.0 0.84 0.83 120 49 171.2 12.04 11.80
12 -11 13.2 0.93 0.91 125 52 184.6 12.98 12.73
14 -10 14.5 1.02 1.00 130 54 198.7 13.97 13.70
16 -9 15.8 1.11 1.09 135 57 213.6 15.02 14.73
18 -8 17.1 1.20 1.18 140 60 229.2 16.11 15.80
20 -7 18.5 1.30 1.28 145 63 245.6 17.27 16.93
22 -6 19.9 1.40 1.37 150 66 262.9 18.48 18.13
24 -4 21.4 1.50 1.48 155 68 281.1 19.76 19.37
26 -3 22.9 1.61 1.58

SECTION 5
ELECTRICAL
5-1 INTRODUCTION
This section includes electrical wiring schematics covering the models listed in Table 1-2. For applications with
OEM supplied operating switches, the switches are wired to the Logic Board connector J3 as shown. For units
with a Micromate control panel as the operators control, there is no wiring to the Logic Board J3 connector,
instead the Micromate control panel is hard wired to the Logic Board connector J2. When the micromate
control panel is used for service or diagnostic purposes, it is wired in the same manner as shown for drivers panel
use, thru the optional Service Port. Contact your Mobile Climate Control service representative or call the
technical hot line at 800-450-2211 for questions related to the schematic for your specific model.

98--63069
Figure 5-1. Wiring Schematic - Legend (PM Motors) - 68AC353-102, 102-4, 102-5

`
98--63069
Figure 5-2. Wiring Schematic - Control Circuit (PM Motors) - 68AC353-102, 102-4, 102-5

`
98--63069
Figure 5-3. Wiring Schematic - Power Circuit (PM Motors) - 68AC353-102, 102-4, 102-5

98--63098
Figure 5-4. Wiring Schematic - Legend (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6

`
98--63098
Figure 5-5. Wiring Schematic - Control Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6

`
98--63098
Figure 5-6. Wiring Schematic - Power Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6

`
98--63098
Figure 5-7. Wiring Schematic - Condenser Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6

`
98--63098
Figure 5-8. Wiring Schematic - Evaporator Circuit (Brushless Motors) (CAN) - 68AC353-102-1, 102-3, 102-6

98--63116
Figure 5-9. Wiring Schematic - Legend (Brushless Motors) - 68AC353-102-2 & 102-7

`
98--63116
Figure 5-10. Wiring Schematic - Control Circuit (Brushless Motors) - 68AC353-102-2 & 102-7

`
98--63116
Figure 5-11. Wiring Schematic - Control Board Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7

`
98--63116
Figure 5-12. Wiring Schematic - Condenser Motor Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7

`
98--63116
Figure 5-13. Wiring Schematic - Evaporator Motor Power Circuit (Brushless Motors) - 68AC353-102-2 & 102-7

A Evaporator Section, 1-7
Exit Alarm Queue, 3-2
Air Filter, 4-13
AIR FLOW, 1-10
Alarm, 2-4, 3-1
F
Alarm Clear, 3-1 Filter-Drier, 4-10
Fresh Air System, 1-7
Alarm Codes, 3-1
Fuse, 1-9
Alarm Queue, 3-1
Ambient Lockout, 1-9
H
B Heating Cycle, 1-13
Heating Mode, 2-3
Boost Pump, 2-3
High Pressure Switch, 1-8, 1-9, 4-9
Hour Meter, 2-4
C
Circuit Breaker, 1-9, 1-18 I
Clutch, 2-4, 4-14, 4-15 INTRODUCTION , 1-1
Compressor, 1-4, 1-8, 4-13
Condenser Fan, 1-8, 2-4 L
Condensing Section, 1-6
LEAK CHECK, 4-7
CONFIGURATION IDENTIFICATION, 1-1
Liquid Line Solenoid, 2-4, 4-11
Control Panel, 1-21 Logic Board, 1-16, 2-1, 3-1, 4-19
Cooling Mode, 2-3 Low Pressure Switch, 1-8, 1-9, 4-9
D M
DESCRIPTION, 1-1 Maintenance Schedule, 4-1
Diagnostics, 2-1, 2-4, 2-5 Micrormate Control Panel, 2-1, 3-1
Discharge Check Valve, 1-4 Modes Of Operation, 2-2
Discharge Pressure, 2-4
N
E Noncondensibles, Check For, 4-9
Evacuation, 4-8
Evacuation, One Time, 4-8 O
Evacuation, Triple, 4-8 Oil Level, 4-16
Evaporator Fan, 1-8, 2-4 Operating Controls, 1-8

Operating Instructions, 2-1 System Parameters, 2-5
OPTION DESCRIPTION, 1-1 System Shutdown, 2-1
System Start-up, 2-1
P
Pre-Trip Inspection, 2-2 T
Pressure Transducer, 1-9, 4-17, 4-18 Temperature Control, 2-3
Pump Down, 4-4, 4-7 Temperature Pressure Chart, 4-20
Temperature Sensor, 1-9, 4-17, 4-18
R Thermostatic Expansion Valve, 1-8, 4-12
Refrigerant Charge, 1-8, 4-4, 4-8, 4-9 Top Cover, 4-2
Refrigerant Removal, 4-5, 4-7 Troubleshooting, 3-1
Refrigeration Cycle, 1-11 Troubleshooting No CAN Communication, 3-2
Relay Board, 1-17, 1-18, 1-19
Relay Board - GR60, 1-17, 1-18 U
Rooftop Unit, 1-5
Unloader Control, 2-3
S
V
SAFETY DEVICES, 1-9
Vent Mode, 2-3
Self Diagnostics, 3-1
SERVICE, 4-1
Service Valves, 4-3 W
Suction Pressure, 2-3 Water Temperature Switch, 1-8, 1-9
Superheat, 4-12 Wiring Schematics, 5-1

Every driver deserves the best possible
vehicle climate with MCC products
MCC provides exceptional performance in mobile climate comfort.
www.mcc-hvac.com
Member of MCC Group S Certified ISO 9001 and ISO 1 4001.
Specifications subject to change without notice. MCC is a registered trademark.
© 2012 Mobile Climate Control T-348 Rev. 07/2012

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T-348 Manual

OPERATION AND SERVICE

© 2012 Mobile Climate Control

© 2012 Mobile Climate Control 1 T-348 Rev. 07/2012

© 2012 Mobile Climate Control 2 T-348 Rev. 07/2012

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© 2012 Mobile Climate Control Safety-1 T-348 Rev. 07/2012

© 2012 Mobile Climate Control Safety-2 T-348 Rev. 07/2012

© 2012 Mobile Climate Control Safety-3 T-348 Rev. 07/2012

© 2012 Mobile Climate Control 1--1 T-348 Rev. 07/2012

© 2012 Mobile Climate Control 1--2 T-348 Rev. 07/2012

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1. Compressor 8. Main Harness

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1. Top Cover, Condenser 4. Evaporator Section (See Figure 1-4)

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1. Coil Assembly 5. Liquid Line

© 2012 Mobile Climate Control 1--6 T-348 Rev. 07/2012

1. Evaporator Coil Assembly 8. Discharge Line

1.4.6 Fresh Air System

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Through Condenser CONDENSER Through Condenser

Figure 1-5 System Air Flow

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1. Discharge Service Valve

Figure 1-6 Refrigerant Flow Diagram

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COOLANT HEAT VALVE (Normally Closed)

Figure 1-7 Heat Flow Diagram

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1. Logic Board (See Figure 1-10) 4. Fresh Air

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With CAN With/Out CAN

1. Logic Board (See Figure 1-10) 5. Fuses

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J1 Logic board power in. J7 Diagnostics interface (RS232, DB9).

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Figure 1-11. Relay Board - GR60

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1.15 RELAY BOARD - GR60, 24VDC (Continued)

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Pin Function Remarks Pin Function Remarks

Figure 1-13 Logic Board, Data Communications

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1. Display 7. HEAT (Only) Button

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© 2012 Mobile Climate Control 2--1 T-348 Rev. 07/2012

REHEAT DUTY CYCLE VENT

--5°F HEAT --5°F HEAT

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