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 freezing point. As warm damp air passes over the fins of 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 recirculate, only air from the passenger compartment passes through the evaporator. As the passenger compartment air dehumidifies, A/C performance levels rise.

CAUTION: Review safety precautions and warnings before proceding with this procedure. Air temperature in test room and on vehicle must be at least 21°C. (70°F.) for this test.

NOTE: When connecting the service equipment coupling to the line fitting, verify that 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.

Attaching Thermocouple Clamp To Liquid Line:

2. Attach a thermal couple to the evaporator line.
3. Set controls:

MANUAL A/C
- A/C on
- Panel recirculation
- Temperature to full cold
- High blower

Automatic Temperature Control (ATC) System
- Rotate blower knob to high position (full clockwise)
- Rotate temperature knob to full cold position (full counter clockwise)
- Push panel mode button
- Push RECIR (Recirculation) button (A/C and RE buttons should be lit)

NOTE: The word AUTO should not appear in the ATC display, confirming that the system is set manually.

1. Start the engine and hold at 1000 rpm with the A/C clutch engaged.
2. Engine should be warmed up with the doors and windows closed.
3. Insert and thermometer in the left center A/C outlet and operate the engine for five minutes. The A/C clutch may cycle depending on ambient conditions.

A/C Performance Chart:

4. With the A/C clutch engaged, compare the discharge air temperature to the A/C performance temperature chart.