Component Tests and General Diagnostics

The cooling performance of the air conditioner changes considerably with changes in surrounding conditions. To check for correct system operation, follow procedure outlined below:
1. Park the vehicle indoors or in the shade.
2. Open all the windows in the vehicle, keeping doors closed.
3. Connect manifold gauge set to high and low side service valves of the system.
4. Set mode switch to A/C MAX position, then air inlet control switch to CIRC.
5. Set temperature lever to COLD position.
6. Start engine and hold speed at 1,500 RPM.
7. After the air conditioner has been operating for 10 minutes, measure system pressures at high pressure (discharge side) and low pressure (suction) side.
8. Measure the temperatures of inlet air to blower and outlet air at the dash panel grilles.
9. Measure the temperature and humidity of the ambient air at a point 3.3 feet from the front of the condenser.

Fig. 1 Air Conditioning System Performance Chart:

Fig. 3 Air Conditioning System Performance Chart:

10. Check for any abnormalities by comparing the test results with standard pressure in performance charts Fig. 1 and 3.
11. The pressure will change in the following manner with changes in the conditions:
a. When blower speed is low, discharge pressure will drop.
b. When the humidity of intake air is low, discharge pressure will drop.
12. The temperature will change in the following manner with changes in conditions:
a. When ambient air temperature is low, the outlet air temperature will become low.