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 the ignition off. Install the ACR 000 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-side and high-side pressures within the specified value?
   • More than 60°F (16°C) - 50 psi (345 kPa).
   • More than 75°F (24°C) - 70 psi (483 kPa).
   • More than 90°F (33°C) - 100 psi (690 kPa).
   If so, go to next step. If not, check system for a refrigerant leak. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING.
NOTE: This step measures the performance of the A/C system. 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 000 Air Conditioning Service Center.
2. Close the vehicle doors and windows. Open the driver door window 5-6 in. (12.7-15.2 cm). Select the following HVAC control settings:
   • Turn the A/C on.
   • Select RECIRCULATION mode.
   • Select maximum blower speed.
   • Air directed through the I/P panel outlets.
   • The coldest temperature setting.
   • All A/C outlets open.
   Install the temperature probes of the ACR 2000 Air Conditioning Service Center in the left and right center A/C air outlets. Apply the parking brake. Place the transaxle in the PARK position. Start the engine. Operate the A/C system for 5 minutes. Inspect a/c components for abnormal frost areas and unusual noises. Print the outlet air temperatures, the low-side pressure and the high-side pressure. Compare the low and high-side pressures and the output temperatures 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 temperatures again.
   • Compare the low and high-side pressures and the 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  8. If not, go to next step.
4. Do the high and low-side pressures fall within the specified ranges, but the outlet temperatures do not? If so, go to A/C PRESSURE ZONE "A" DIAGNOSIS  under SYSTEM TESTS. 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  under SYSTEM TESTS. 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  under SYSTEM TESTS. 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  under SYSTEM TESTS. 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 TROUBLE SHOOTING .

Fig 1: A/C Performance Table

Courtesy of GENERAL MOTORS CORP.