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A/C System Performance Test

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NOTE: Tools Required: ACR 2000 Air Conditioning Service Center (J-43600).
NOTE: The ambient air temperature must be at least 60°F (16°C). Do not induce additional air flow across the front of the vehicle during the test.
NOTE: If you were sent here from a DTC diagnostic table, clear the DTC upon completion of this test.
NOTE: This step determines if the A/C system has at least the minimum refrigerant charge required to operate the system without damage.
  1. Park the vehicle inside or in the shade. Open the windows in order to ventilate the interior of the vehicle. If the A/C system was operating, allow the A/C system to equalize for about 2 minutes. Turn ignition off. Install ACR 2000 Air Conditioning Service Center. Record the ambient air temperature displayed on the ACR 2000 Air Conditioning Service Center. Record the low and high side static pressure readings. Are both the low and high side pressures greater than:
    • 60°F (16°C), 50 psi (345 kPa).
    • 75°F (24°C) 70 psi (483 kPa).
    • 90°F (33°C), 100 psi (690 kPa).
    If so, go to next step. If not, See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING.
    2. NOTE: Record the relative humidity and the ambient air temperature at the time of the test.
    NOTE: Press the reset button, before using the print function of the ACR 2000 Air Conditioning Service Center.
  2. Close the vehicle doors and windows. Open the drivers door window 5-6 inches (127-152 mm). Turn the A/C on, select the coldest temperature setting, the maximum blower speed and the I/P panel outlet mode HVAC control settings. All I/P panel outlets are open. Select recirculation mode. Install the temperature probes to the ACR 2000 Air Conditioning Service Center in the left and right center A/C air outlets. Apply the parking brake. Place the transmission in the Park or Neutral. Start the engine. Operate the A/C system for 5 minutes. Inspect A/C components for the abnormal frost areas and unusual noises. Print the panel outlet air temperatures, the low-side pressure and the high-side pressure. Compare the low and high side pressures and the panel output temperatures to the tables. See Fig 1 or Fig 2 . Does all the data recorded fall within the specified ranges of the tables? If so, go to step  8. If not, go to next step.
    3. NOTE: This step is to allow for vehicle variations as well as high ambient air temperatures.
  3. If the pressures and temperatures recorded do not fall within the specified ranges. Continue to operate the A/C system for an additional 5 minutes. Reset the ACR 2000 Air Conditioning Service Center and record the pressures and temperatures again. Compare the low and high side pressures and the output temperature to the tables. See Fig 1 or Fig 2 . Does all the data recorded fall within the specified ranges of the tables? If so, go to step  8. If not, go to next step.
  4. Do the high and low side pressures fall within the specified ranges but the panel outlet temperatures do not? I so, go to A/C PRESSURE ZONE "A" DIAGNOSIS . If not, go to next step.
  5. Is the low side pressure greater than the specified range but the high side pressure within or less than the specified range? If so, go to A/C PRESSURE ZONE "B" DIAGNOSIS . If not, go to next step.
  6. Are the low and high side pressures both greater than the specified ranges? If so, go to A/C PRESSURE ZONE "C" DIAGNOSIS . If not, go to next step.
  7. Is the high side pressure greater than the specified range, but the low side pressure is within or less than the specified range? If so, go to A/C PRESSURE ZONE "D" DIAGNOSIS . If not, go to next step.
  8. Operate the system in order to verify the test results. Did you find the same results? If so, system is okay. If not, See SYMPTOM TESTS .
    Fig 1: A/C System Performance Table Without Rear A/C
    G00218163Courtesy of GENERAL MOTORS CORP.
    Fig 2: A/C System Performance Table With Rear A/C
    G00218164Courtesy of GENERAL MOTORS CORP.
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