Refrigerant System Checks

Refrigerant System Diagnosis

Pressure-Temperature Relationship Of R-134a:

Functional Test

To aid in determining whether or not the electrical, vacuum, and refrigeration systems are operating properly refer to the following:

1. Operation of the air conditioning modes and blower at all speeds with the mode lever in any position expect "OFF" and engagement of the compressor clutch would indicate that the electrical circuits are operating properly.
2. The same "hand felt" temperature of the evaporator inlet pipe and the accumulator surface of an operating system would indicate a properly charged system.

Performance Test

Tool Required
- J 21213-A Four Jack-Dual Range Temperature Tester of Equivalent

1. Park vehicle inside or in a shaded area.
2. Open door or windows to ventilate interior.
3. Vent engine exhaust, if necessary.
4. Open the good and install high and low side pressure gages. Route the lines over the rear hood seal, and tape the gages to the windshield for viewing.
5. Close the hood to the safety latch position.
6. Record the ambient temperature at the vehicle.
7. Record relative humidity. Use psychrometer or consult local weather bureau.
- Be sure to record relative humidity and ambient temperature conditions at time of test.
8. Close doors or windows.
9. Set mode control to MAX A/C, adjust blower speed to HI and temperature to full cold.
10. Open air conditioning outlets.
11. Install J 21213-A or equivalent into right center air conditioning outlet.
12. Place transmission in PARK or NEUTRAL.
13. Start engine, stabilize engine speed at 1500 RPM, and start the timer.
14. Run the air conditioning system until outlet air reaches the lowest temperature (about 3 minutes).
15. Record outlet air temperature and high-side and low-side pressures.
16. Turn the engine off and compare the readings. Normally operating air conditioning systems should not exceed the levels shown.

Inspect

If a malfunction in the refrigerant system is suspected due to abnormal system pressures, inspect the following:

1. Outer surfaces of radiator and condenser cores. Make sure airflow is not blocked my dirt, leaves or other foreign material. Be sure to check between the condenser and radiator as well as the outer surfaces.
2. Evaporator core, condenser core, hoses, tubes, etc. for restrictions and kinks.
3. Refrigerant leaks.
4. All air ducts for leaks or restrictions. Low air flow rate may indicate a restricted evaporator core.
5. Compressor clutch for slippage.
6. Drive belt for improper tension. If the problem is not found, continue with diagnostic procedures in Symptom Testing.

Vacuum System

Start the engine and allow it to idle. Move the rotary knobs to each position and refer to the vacuum diagrams and operation charts for airflow, air door functioning, and vacuum circuits. If airflow is not out of the proper outlet at each rotary knob position doe the following:

1. The hose connections at the vacuum actuator's control head valve and vacuum tank.
2. The vacuum source circuit:
- Install a vacuum tee and gage (with restrictor) at the vacuum tank outlet. Idle the engine and read the vacuum. At all selector lever positions, normal vacuum is equivalent to manifold vacuum.
- If vacuum is less than normal at all positions remove the tee and connect the vacuum gage line to the tank and read the vacuum. If still low, then the problem lies in the feed circuit, the feed circuit to the tank or in the tank itself. If vacuum is now normal, then the problem lies downstream.
- Vacuum may be less than normal at some positions. If vacuum was low at one or several of the selector lever positions, a leak is indicated in these circuits.
- Vacuum may be normal at all positions. If vacuum was normal and even at all positions, then the malfunction may be caused by improperly connected or plugged or split lines or a malfunctioning vacuum valve or valves.
3. Specific vacuum circuit check:
- Place the rotary knob in the malfunctioning position and check for vacuum at the pertinent vacuum actuator's.
- If vacuum exists at the actuator but the door does not move, then the actuator is defective or the door is mechanically bound.