A/C Performance Testing

The air conditioning system is designed to remove heat and humidity from the air entering the passenger compartment. The evaporator, located in the heater A/C unit, is cooled to temperatures near the freezing point. As warm damp air passes over the fins in the evaporator, moisture in the air condenses to water, dehumidifying the air. Condensation on the evaporator fins reduces the evaporators ability to absorb heat. During periods of high heat and humidity, an air conditioning system will be less effective. With the control module set to RECIRC, only air from the passenger compartment passes through the evaporator. As the passenger compartment air dehumidifies, A/C performance levels rise.

Performance Test Procedure
Review Safety Precautions and Warnings before proceeding with this procedure. Air temperature in test room and on vehicle must be 21 degree Celsius (70 degree Fahrenheit) minimum for this test.

NOTE: When connecting the service equipment coupling to the line fitting, verify that the valve of the coupling is fully closed. This will reduce the amount of effort required to make the connection.

1. Connect a tachometer and manifold gauge set. Attach a thermocouple to the evaporator inlet line.
2. Set control to A/C, RECIRC, and PANEL, temperature lever on full cool and blower on high.
3. Start engine and hold at 1000 rpm with A/C clutch engaged.
4. Engine should be warmed up with doors and windows closed.
5. Insert a thermometer or place a thermocouple in the left center A/C outlet and operate the engine for 5 Minutes. The A/C clutch may cycle depending on ambient conditions.
6. With the A/C clutch engaged, compare the discharge air temperature to the evaporator inlet line temperature. The evaporator inlet line temperature should be no more than 12 degree Celsius (10 degree Fahrenheit.) cooler than the discharge air temperature.
7. If the discharge air temperature fails to meet the specifications. Refer to the System Charge Level.