A/C Performance Test

This test measures the operating efficiency of the A/C system under the following conditions:

• The current ambient air temperature.
• The current relative humidity.
• The high side pressure of the A/C system.
• The low side pressure of the A/C system.
• The temperature of the air being discharged into the passenger compartment.

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 the 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. If both the low side 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)
   go to next step. If not, check for a leak. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING.
NOTE: This step measures the performance of the A/C system.
2. Record the relative humidity and the ambient air temperature at the time of the test. Press the reset button before using the print function of the ACR 2000 Air Conditioning Service Center. Close the vehicle doors and windows. Open the drivers door window 5-6" (12.7-15.2 cm). Select A/C setting RECIRCULATION mode, maximum blower speed, PANEL mode, coldest temperature setting and all panel outlets are Open HVAC control settings. Install the temperature probes of the ACR 2000 Air Conditioning Service Center in the left and right center panel air outlets. Apply the parking brake. Place the transaxle in Park. Start the engine. Operate the A/C system for 5 minutes. Inspect A/C components for abnormal frost areas or unusual noises. Print the panel outlet air temperature, the low-side pressure, the high-side pressure and compare the low and high side pressures and the panel output temperature to the table. See Fig 1 . Does all the data recorded fall within the specified ranges of the table? If so, go to step  4 . If not, go to next step.
NOTE: This step is to allow for vehicle variations as well as high ambient 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 temperature again. Compare the low and high side pressures and the panel output temperature to the table below. Does all the data recorded fall within the specified ranges of the table, see Fig 1 ? 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 temperature do not? If 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 okay. If not, go to TROUBLESHOOTING  .

Fig 1: A/C Performance Table

Courtesy of GENERAL MOTORS CORP.