Tutorial Guide To Manifold Gauges

A Tutorial Guide to Manifold Gauges
Before servicing a vehicle, confirm system refrigerant type. Cross contamination of refrigerants can cause
damage to A/C system, service tools and equipment.
GENERAL MANIFOLD INFORMATION:
The right (red) side of the manifold is the high side and the red gauge is the high pressure gauge. The left (blue) side
of the manifold is the low side and the blue gauge is the vacuum/pressure gauge. Separate passages from the low and
high side fittings to their respective gauges allow one to check pressure and vacuum readings. The manifold body
connects all three fittings to each other by internal passages.
Note: If gauges do not read 0 psi, remove gauge face and adjust calibration screw to 0 psi.
Caution: Never open the high side valve on manifold gauge set when the A/C System is operating.
SYSTEM OPERATION:
Service couplers must be connected to a refrigerant hose and the refrigerant hose must be connected to a
manifold gauge set with both low and high side valves in the closed position before connecting the couplers to
an A/C System.
1stClose all valves on the manual service couplers and manifold gauge set. Connect the high side
coupler to the high side port and connect the low side coupler to the low side port.
2nd Start the vehicle. Turn on the A/C system, and let it run until gauge readings stabilize.
3rd If the pressure shown on the gauges differ from the manufacturer’s specs, determine the
problem and make necessary repairs.
SYSTEM EVACUATION:
1stRecover all refrigerant from the system. DO NOT VENT REFRIGERANT TO THE
ATMOSPHERE, USE APPROPRIATE RECOVERY EQUIPMENT.
2nd Connect the BLUE hose to the low side service port. Connect the RED hose to the high side
service port. Connect the YELLOW hose to a vacuum pump.
3rd Open the HIGH and LOW manifold valves using the Red and Blue hand valves and start the
pump.
4th After evacuating the system according to the manufacturer’s specs, close both valves and turn
off the vacuum pump. Disconnect the YELLOW charging hose from the vacuum pump and connect
it to the appropriate refrigerant container.
5th After all connections have been made, the refrigerant can be added through the low side per
manufacturer’s specifications.
CHARGING AN EMPTY SYSTEM:
1stVehicle engine the A/C system must both be off.
2nd Make certain that the dispensing valve on the refrigerant source is in the closed position.
3rd Make certain that both the high pressure and the low pressure valves are in their closed position.
4th Connect both high and low couplers to the A/C system’s service ports. After connecting the
couplers, open them by turning the knob on the top of it clockwise until it stops.
5th Open valve on the refrigerant source.
6th Open the low side valve on the manifold gauge set.
7th Charge system until gauges read over 50 pounds of pressure.
8th Close low side valve on the manifold gauge set.
9th Turn off High Side and Low Side valves on the manifold gauge set.
10th Go to step # 4 in Charging an A/C System that is low on Refrigerant (below)
CHARGING AN A/C SYSTEM THAT IS LOW:
1stMake certain that the dispensing valve on the refrigerant source is closed.
2nd Make certain that both the high pressure and the low pressure valves are closed.
3rd Connect both couplers to the system’s service ports. Afterwards, open them by turning the knob
on the top of the coupler until it stops.
4th Start the vehicle. Ensure adequate air flow through the front of the vehicle to avoid overheating.
5th Turn on the A/C and set controls for MAX COOL and high fan.
6th Open the dispensing valve on the refrigerant source. (Keep the refrigerant source upright at all
times so that refrigerant can only enter the hoses as a gas.) To begin adding refrigerant (with system
running) open the BLUE low side valve. Allow the gas to flow into the system until the desired
amount has been added or until the source container is empty. Getting the required refrigerant
amount into the system may take several minutes.
7th When you have charged the system to manufacturer’s specs, close the manifold’s blue valve.
Let the compressor run and check the gauge readings to be sure the system is operating properly. If
not, repair the system as required by manufacturer’s service manual.
8th To disconnect the manifold when the system is filled and operating properly, close the BLUE
(low side) and RED (high side) hand valves on the manifold.
9th To disconnect the manual coupler, turn the knob on it until finger tight. Slide the coupler sleeve
up, releasing the coupler from the vehicle’s service port.
10th Replace protective caps on vehicle’s service fittings.
LMK 2019

Tutorial Guide To Manifold Gauges

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