A/C System Performance Test - HVAC System - Manual
System Performance TestIMPORTANT: Be sure to record the relative humidity and ambient temperature conditions at the time of the test.
1. Park the vehicle inside or in the shade. The ambient temperature must be at least 21°C (70°F).
2. Open the windows to ventilate the interior.
3. Vent the engine exhaust.
4. Open the hood and install the high and low side pressure gauges.
5. Route the pressure gauge hoses and close the hood to the safety latch position.
6. Record the ambient temperature outside.
7. Record the relative humidity.
8. Turn the A/C on, set the mode to vent, the temperature to full cold, the fresh/recirc to recirculation, the blower speed to high and the windows open.
9. Open the A/C air outlet deflectors.
10. Place a thermometer in the left center A/C outlet.
11. Place the transaxle in PARK and start the engine, stabilize the engine at 1500 RPM.
12. Run the A/C system until the outlet air reaches the lowest temperature (about 5 minutes).
13. Record the outlet air temperature and the high side and low side pressures.
14. Turn the engine off and compare the readings with the data in the A/C Performance Table. Normally operating A/C system should not exceed levels shown.
15. If the readings exceed the table limits, refer to VDOT A/C System Diagnosis. Also refer to HVAC System Check. Initial Inspection and Diagnostic Overview System Check - HVAC System - Manual
This table indicates the pressure of the Refrigerant-134a at various temperatures.
For instance, a drum of refrigerant at room temperature of 26.6°C (80°F) will have a pressure of 595.6 kPa (86.4 PSI). If the refrigerant is heated to 51.6°C (125°F), the pressure will increase to 1278.8 kPa (185.5 PSI).
The refrigerant also can be used conversely in order to determine the temperature at which the Refrigerant-134a boils under various pressures. For example, at a pressure of 188.2 kPa (27.3 PSI). The Refrigerant-134a boils at 0°C.