Refrigerant System Performance Check

Fig. 1 System Pressure & Temperature Chart:

The most common complaints associated with an air conditioning system are inadequate, erratic or non-existent cooling. To diagnose a fault correctly, proceed as follows:
1. Connect a manifold gauge set.
2. Close both hand valves on manifold gauge set.
3. Select A/C system controls to obtain maximum cooling.
4. Place a thermometer approximately 1/4 into center vent nozzle.
5. Apply parking brake, close all windows and doors and run engine at 1500 RPM for approximately three minutes.
6. Read the temperature on the thermometer. The temperature should be within specifications, which vary according to ambient air temperature, Fig. 1.
7. Compare manifold gauge readings with specifications, Fig. 1., then proceed to proper diagnosis and match test results.