Auxiliary Blower Motor Malfunction

Auxiliary Blower Motor Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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.

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

Blower Motor Malfunction
1. Ignition OFF, disconnect the harness connector at the auxiliary HVAC control module.
2. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal A4 and ground.

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

3. Ignition ON, place the auxiliary blower motor in each speed position. Verify that a test lamp does illuminate between each control circuit terminal for the proper switch position and ground.

^ If the test lamp does not illuminate, test the appropriate control circuit for a short to ground, open or high resistance.

4. Ignition ON, place the auxiliary blower in the high speed position. Connect a test lamp between the control circuit terminal 2 and the ground circuit terminal 1 at the blower motor.

^ If the test lamp is OFF, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the blower motor.

Component Testing

Blower Motor
1. Ignition OFF, disconnect the harness connector at the blower motor.
2. Install a 30-amp fused jumper wire between the relay controlled output circuit terminal A and 12 volts. Install a jumper wire between the control circuit terminal B 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 after completing the diagnostic procedure. Verification Tests

* Auxiliary Blower Motor Replacement
* Blower Motor Resistor Assembly Replacement