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A/C Pressure Zone "A" Diagnosis

WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
NOTE: Tools Required: ACR 2000 Air Conditioning Service Center (J-43600) or equivalent.
  1. Were you sent here from the A/C PERFORMANCE TEST? If so, go to next step. If not, go to A/C PERFORMANCE TEST  under PERFORMANCE TESTS.
  2. Refer to the panel air outlet temperatures recorded during the A/C PERFORMANCE TEST. Did you find a difference of greater than 2-3°F (1-2°C) in the discharge air temperature between the right and left center I/P outlets? If so, go to step  7. If not, go to next step.
  3. Did the customer state that the A/C system panel mode output temperatures are good at first, but then turn warm during extended drives? If so, go to next step. If not, go to step  5.
  4. Increase engine speed to 2000 RPM. During extended operation of the A/C system, does the low-side pressure decrease, possibly accompanied by heavy frost on the liquid line between the orifice tube and the evaporator? If so, go to A/C PRESSURE ZONE "D" DIAGNOSIS . If not, go to next step.
  5. Refer to the pressures recorded during the A/C PERFORMANCE TEST. Inspect for the following conditions:
    • The high-side pressure is slightly greater than the specified pressure ranges but still within zone "A" on the A/C Pressure-Zone Classification Chart. See Fig 1.
    • The discharge line is hot.
    • The suction line is cool.
    Do the listed conditions exist? If so, go to step  7. If not, go to next step.
  6. Refer to the pressures recorded during the A/C PERFORMANCE TEST. Inspect for the following conditions:
    • The low-side pressure is slightly less than the specified pressure ranges but still within zone "A" on the A/C Pressure-Zone Classification Chart. See Fig 1.
    • The discharge line is warm-to-hot.
    • The suction line is cool-to-warm.
    Do the listed conditions exist? If so, go to step  8. If not, go to TEST J: TOO HOT IN VEHICLE  under SYMPTOM TESTS.
  7. The A/C system may be undercharged. Leak test A/C system. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Recharge the A/C system to specifications. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to step  14.
  8. The A/C system may be contaminated. Using the ACR 2000 Air Conditioning Service Center view the information screen for detection of foreign gases in the A/C system. Do foreign gases exist? If so, go to next step. If not, go to step  10.
  9. Evacuate the A/C system to a scavenging tank. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Recharge the A/C system to specifications. After repairs are complete, go to step  14.
  10. The A/C system may contain too much moisture or air. Evacuate and recharge the A/C system to specifications. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Operate the A/C system and check the outlet air temperatures. See A/C PERFORMANCE TEST  under PERFORMANCE TESTS. Are the outlet temperatures within the specified ranges of the A/C Performance Test Table? See Figure. If so, go to step  15. If not, go to next step.
  11. The A/C system may contain too much refrigerant oil. Recover the refrigerant from the A/C system. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Remove the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Drain and measure the refrigerant oil from the accumulator. Did you drain greater than 5 oz. (148 ml) of refrigerant oil from the accumulator? If so, go to next step. If not, go to step  13.
  12. Reinstall the accumulator. Flush the A/C system. See FLUSHING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Add the specified amount of refrigerant oil to the accumulator. See SPECIFICATIONS . Recharge the A/C system. After repairs are complete, go to step  14.
  13. Add the specified amount of refrigerant oil to the accumulator. See SPECIFICATIONS . Install the accumulator. Recharge the A/C system. After repairs are complete, go to step  14.
  14. Record the low and high-side pressures and the I/P panel outlet air temperature. Compare the outlet temperatures to those listed in the A/C System Performance Chart. See Fig 1. Are the high and low-side pressures and outlet temperatures within specifications? If so, go to next step. If not, see A/C PERFORMANCE TEST  under PERFORMANCE TESTS.
  15. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.
Fig 1: A/C Pressure-Zone Classification Chart
G00194579Courtesy of GENERAL MOTORS CORP.
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