Rear Booster Fan Runs At Only One Speed (ATC)

*REAR BOOSTER FAN RUNS AT ONLY ONE SPEED (ATC)

For a complete wiring diagram Consult Diagrams/Electrical





Diagnostic Test

1. OPERATE REAR BOOSTER FAN & CHECK FOR HVAC DTCs
Turn the ignition on.
Press the A/C Heater Control's PWR switch on.
Press the REAR fan mode switch on so that it is in manual mode. The word "REAR" should display on the A/C Heater Control display panel. The word "AUTO" should not be displayed.
Turn the Rear Booster Fan Rear Control switch to AUTO for 30 seconds. Then, slowly turn it from AUTO to high speed and then back to AUTO.
With the scan tool, read HVAC DTCs.
Does the scan tool display any DTCs?

Yes

- Diagnose and Repair the DTC(s).

No

- Go To 2

2. CHECK (C57) REAR BOOSTER FAN CONTROL CIRCUIT FOR A SHORT TO GROUND
Turn the ignition off.
Disconnect the Rear Booster Fan Power Module C1 harness connector.
Disconnect the A/C Heater Control harness connector.
Measure the resistance between ground and the Rear Booster Fan Control circuit.
Does the scan tool read open circuit?

Yes

- Go To 3

No

- Repair the (C57) Rear Booster Fan Control circuit for a short to ground.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

3. CHECK A/C HEATER CONTROL OPERATION
Reconnect all previously disconnected components.
Turn the ignition on.
With the scan tool, check the data display for the Front Blower with the A/C Heater Control in the lowest and highest settings.
Does the scan tool display approximately 32.0% in the lowest setting and 100% in the highest setting?

Yes

- Replace the Front Blower Power Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Replace the A/C Heater Control.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.