A/C Performance Test

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 dehu-midifies, A/C performance levels rise.

PERFORMANCE
Review all Warnings before proceeding with this procedure. Air temperature in test room and on vehicle must be 21° C (70° F) 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 or a A/C Charging/Recycling Station. Attach a thermocouple to the evaporator outlet line.
2. Set controls:

MTC (Manual Temperature Control) System:
- A/C ON
- Panel Recirculation
- Temperature to full cold
- High blower

ATC (Automatic Temperature Control) System:
- Rotate blower knob to high position (full clockwise)
- Set temperature to the LO position
- Push panel mode button
- Push RECIRC (Recirculation) button (A/C and RECIRC symbols should be lit)

NOTE: The word MANUAL should appear in the ATC display, confirming that the system is set manually.

3. Start engine and hold at 1000 rpm with A/C dutch 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 five minutes. The A/C clutch may cycle depending on ambient conditions.

A/C Performance Temperature And Pressure:

6. With the A/C dutch engaged, compare the discharge air temperature to the A/C Performance Temperature table.