System Performance Test

Figure 1 Pressure-Temperature Relationship Of Refrigerant-134a:

Figure 2 System Performance Test:

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

1. Park the vehicle inside or in a shaded area.
2. Open doors or windows to ventilate the interior.
3. Vent engine exhaust if necessary.
4. Open the hood and install ACR4 high and low side pressure gages.
5. Record ambient temperature at the vehicle.
6. Record relative humidity. Use a psychrometer or consult the local weather bureau.

Note: Make sure to record relative humidity and ambient temperature conditions at time of test.

7. Close doors or windows.
- For Suburban models with rear A/C, turn rear A/C "ON."
8. Press the "A/C" button, adjust blower speed to "HI," and temperature to full "COLD."
9. Open the air conditioning outlets.
10. Install J 21213-A or equivalent into the right center air conditioning outlet.
11. Place transmission in "PARK" or "NEUTRAL."
12. Start engine, stabilize engine speed at 2000 RPM, and start the timer.
13. Run the air conditioning system until outlet air reaches the lowest temperature (about 3 minutes).
14. Record the outlet air temperature and high side and low side pressures.
15. Turn the engine off and compare the readings. Normally operating air conditioning systems should not exceed the levels shown in Figures 1 and 2.

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 by dirt, leaves, or other foreign material. Check between the condenser and radiator as well as the outer surfaces.
2. Evaporator core, condenser core, hoses, tubes, etc., for restrictions or kinks.
3. Refrigerant leaks.
4. Air ducts for leaks or restrictions. Low airflow rate may indicate a restricted evaporator core.
5. Compressor clutch for slippage.
6. Drive belt for. improper tension.
7. Accumulator for plugging.
8. Expansion (orifice) tube for plugging.

If the problem is not found, refer to Symptom Diagnostic Charts / Insufficient Cooling.