HVAC System Test

HVAC SYSTEM TEST

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The HVAC System Test provides a starting point in the diagnostic process by identifying the appropriate diagnostic procedure or system test to perform when diagnosing a given symptom, condition, or Diagnostic Trouble Code (DTC). It also provides a means for testing the entire HVAC system by utilizing the A/C Heater Control's On-Board System Tests. The HVAC System Tests can also assist in diagnosing stored DTCs.

1. HVAC SYSTEM TEST

NOTE: Diagnose and repair all active DTCs before diagnosing and repairing stored DTCs. If active DTCs are present Testing and Inspection and perform the appropriate diagnostic procedure.

Make a selection based on the symptom, condition, or DTC that you want to diagnose.

Scan Tool Indicates HVAC Not Active On Bus

- No Response From HVAC (A/C Heater Control Module) Perform the No Response from HVAC diagnostic procedure.

Blower Motor Inoperative

- for Blower Motor diagnostic procedures.

Actuator Calibration Test

- Go To 4

A/C System Performance Test

- Go To 2

2. A/C COOLDOWN TEST
The following are prerequisites of the A/C Cooldown Test. Verify that the:

- Refrigerant system has an adequate charge. Check and repair as necessary before proceeding Component Tests and General Diagnostics.
- Blower motor operates correctly in all speeds. Diagnose and repair all blower related faults before proceeding.
- Work area ambient temperature is above 16° C (60° F) before proceeding. Move the vehicle to a warmer work area if necessary.
- Evaporator temperature is above 13° C (55° F) before proceeding.
- A/C compressor is not running. If the compressor is running, turn the A/C off and allow the evaporator to warm up before proceeding.

NOTE: Running the AC Cooldown test will cause the A/C status indicator to flash. One or more status messages will display on the scan tool after running the Cooldown Test. These messages will clear after paging back out of this test function. Therefore, it is important to note all messages before doing so.

1. Start the engine.
2. Turn the Blower control to the high speed position.
3. With the scan tool in HVAC, select System Tests and then select Cooldown test. Allow the test to run to completion.

Does the scan tool display a status message that indicates a fault has occurred?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 3

3. MODE SWITCH AND DOOR ACTUATOR CIRCUIT TEST

NOTE: If at anytime a DTC becomes active during this test, proceed to the conclusion question. If multiple DTCs are active, diagnose those that relate to a short circuit first.

1. Start the engine and turn the Blower control to the low speed position.
2. Set the Blend control (single-zone) or Driver and Passenger Blend control (dual-zone) to the full cold position.
3. Monitor the scan tool for active HVAC DTCs while performing the following test steps.
- If equipped, press the A/C mode switch on, wait 30 seconds, and then press it off.
- If equipped, press the Recirculation mode switch on, wait 30 seconds, and then press it off.
- If equipped, press the EBL mode switch on, wait 30 seconds, and then press it off.
- Move the Blend control (single-zone) or Driver Blend control (dual-zone) from full cold to full hot, wait 30 seconds, and then move it back to full cold.
- If equipped, move the Passenger Blend control from full cold to full hot, wait 30 seconds, and then moved it back to full cold.
- Turn the Mode select control to the defrost position, wait 30 seconds, and then turn it to the panel position (dual-zone) or panel / recirculation position (single-zone). Wait 30 seconds before proceeding.

Does the scan tool display any active DTCs?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 4

4. ACTUATOR CALIBRATION TEST
1. Ignition on, engine not running.
2. With the scan tool, select Actuator Calibration Test. When the test is complete, read HVAC DTCs.

Does the scan tool display any DTCs?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Test Complete.