Auxiliary Blower Motor Malfunction

Auxiliary Blower Motor Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

Low speed is air flowing through the center console ducts being pushed by the front blower motor. Medium speed is controlled by the auxiliary HVAC control module using 1 resistor in series with the blower motor. High speed is also controlled by the auxiliary HVAC control module it applies battery voltage straight to the auxiliary blower motor.

Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Component Connector End Views)
Description and Operation

* Air Temperature Description and Operation (Air Temperature Description and Operation)
* Air Delivery Description and Operation (Air Delivery Description and Operation)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Control Module References) for scan tool information

Circuit/System Verification

Ignition ON, mode selector set to Vent, command the blower motor from MED to HIGH by changing the blower motor switch positions, the blower motor should activate and operate from medium to high when changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the rear blower resistor.
2. Ignition ON, rear blower in the low speed position, verify a test lamp illuminates between the control circuit terminal 2 and ground.

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the auxiliary HVAC control module.

3. Ignition OFF, connect the harness connector at the rear blower resistor. Disconnect the harness connector at the rear blower motor.
4. Test for less than 5 ohms between the ground circuit terminal 1 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

5. Ignition ON, rear blower in the high speed position, verify a test lamp illuminates between the control circuit terminal 2 and ground.

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the auxiliary HVAC control module.

6. Rear blower in the low speed position, verify a test lamp illuminates between the control circuit terminal 2 and ground.

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the rear blower resistor.

7. If all circuits test normal, test or replace the rear blower motor.

Component Testing

1. Ignition OFF, disconnect the harness connector at the rear blower motor.
2. Install a 30-amp fused jumper wire between the control circuit terminal 2 and 12 volts. Install a jumper wire between the control circuit terminal 1 and ground. Verify the blower motor activates.

• If the blower motor does not activate, replace the blower motor.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Auxiliary Blower Motor Replacement (Service and Repair)
* Blower Motor Resistor Assembly Replacement (Service and Repair)
* Control Module References (Control Module References) for auxiliary HVAC control module replacement, setup, and programming