System Performance Test

Fig. 1 Temperature comparison 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. Place A/C system in operation as follows:
a. Close both hand valves on manifold gauge set.
b. Set A/C system to maximum cooling and the fan to ``Speed II'' and ``recirculated air'', then insert a thermometer into the center vent nozzle approximately .2-.28 inch.
c. Apply parking brake, close all windows and doors and run engine at 1500 RPM for approximately 3 minutes.
d. Read the temperature on the thermometer. The temperature should be within specifications, which vary according to ambient air temperature, Fig. 1.

Fig. 2 Low pressure side test pressure range chart:

Fig. 3 High pressure side test pressure range chart:

3. Compare manifold gauge readings with specifications, Figs. 2 and 3, then proceed to proper diagnosis and match test results.