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A/C Pressure Zone "A" Diagnosis

WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. 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 Test Center (J-43600).
  1. Were you sent here from the A/C SYSTEM PERFORMANCE TEST? If so, go to next step. If not, go to A/C SYSTEM PERFORMANCE TEST  under PERFORMANCE TESTS.
  2. Refer to the air outlet temperatures recorded during the A/C system performance test. See Figure and Figure . 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 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 system performance test. See A/C SYSTEM PERFORMANCE TEST  under PERFORMANCE TESTS. Inspect for high side pressure being slightly greater than the specified pressure ranges but still within zone "A". See Figure. If the discharge line is hot or the suction line is cool, go to step  7. If the previous conditions do not exist, go to next step.
  6. Refer to the pressures recorded during the A/C system performance test. See A/C SYSTEM PERFORMANCE TEST  under PERFORMANCE TESTS. Inspect for the following conditions:
    • The low side pressure is slightly less than the specified pressure ranges but still within zone "A". See Figure.
    • 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 SYSTEM 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. Repair as necessary. Recharge the A/C system to specifications. After repairs are complete, go to step  14.
  8. The A/C system may be contaminated. Use ACR 2000 Air Conditioning Test Center to 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. 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.
  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 verify the outlet air temperatures. See A/C SYSTEM PERFORMANCE TEST  under PERFORMANCE TESTS. Are the outlet temperatures within the specified ranges of the A/C Performance Test Table? 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. Remove the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Drain and measure the refrigerant oil from the accumulator. Did you drain greater than 5 ozs. (148 ml) of refrigerant oil from the accumulator? If so, go to next step. If not, go to step  13.
  12. Reinstall the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Flush the A/C system. See FLUSHING PROCEDURES 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. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to step  14.
  13. Add the specified amount of refrigerant oil to the accumulator. See SPECIFICATIONS . Install the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Recharge the A/C system. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to step  14.
  14. Record the low and high side pressures and the I/P outlet air temperature. Compare the outlet temperatures to those listed in the A/C System Performance Chart. See Figure. Are the high and low side pressures and the outlet temperatures within specifications? If so, go to next step. If not, go to A/C SYSTEM 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.
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