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Blower Motor Malfunction




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

The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor speed control from the HVAC control module, battery positive and ground circuits enable the blower motor control module to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the blower motor control module in order to command the blower motor speed. The blower motor control module transfers the PWM signal into a corresponding blower motor voltage. The voltage amounts to between 2-13 V and changes linear to the reading of the PWM signal.

Diagnostic Aids

Check the following mechanical fault sources:

* Air distribution box

* Air distribution hoses/air distribution ducts

Reference Information

Schematic Reference

HVAC Schematics HVAC - Manual

Connector End View Reference

Component Connector End Views Sunshade - Left (DH6)

Description and Operation

Manual HVAC Description and Operation HVAC - Manual

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 Testing

1. Ignition ON, turn the blower motor knob on high speed then to low speed. Verify the scan tool Blower Motor Switch parameter. The reading should correspond to the selected blower step.

• If the parameter does not correspond to the selected blower step
Replace the A26 HVAC Controls.

• If the parameter corresponds to the selected blower step

2. Ignition OFF, disconnect the X1 harness connector at the K8 Blower Motor Control Module.

3. Test for less than 5 ohms between the K8 Blower Motor Control Module ground circuit terminal 5 X1 and ground.

• If greater than 5 ohms
Repair the open/high resistance in the circuit.

• If less than 5 ohms

4. Ignition ON, verify that a test lamp illuminates between K8 Blower Motor Control Module the B+ circuit terminal 6 X1 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Disconnect the harness connector at the M8 Blower Motor and the X2 harness connector at the K8 Blower Motor Control Module.

4. Test for infinite resistance between the B+ circuit terminal 1 X2 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

5. Connect the harness connector at the M8 Blower Motor.

6. Install a jumper wire between the ground circuit terminal 2 X2 and ground.

7. Install a 40 A fused jumper wire between the B+ circuit terminal 1 X2 and B+ and verify the fuse is good.

• If the fuse is open, replace the M8 Blower Motor.

• If the fuse is good, replace the K8 Blower Motor Control Module.

• If the test lamp illuminates

5. Ignition OFF, disconnect the harness connector at the M8 Blower Motor and connect the X1 harness connector at the K8 Blower Motor Control Module, ignition ON.

6. Verify that a test lamp illuminates between the M8 Blower Motor B+ circuit terminal 2 and ground.

• If the test lamp does not illuminate

1. Ignition OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K8 Blower Motor Control Module.

• If the test lamp illuminates

7. Connect a test lamp between the M8 Blower Motor B+ circuit terminal 2 and the M8 Blower Motor control circuit terminal 1.

8. Turn the blower motor OFF. Verify the test lamp does not illuminate.

• If the test lamp illuminates

1. Ignition OFF, disconnect the X2 harness connector at the K8 Blower Motor Control Module. Keep the test lamp still connected.

2. Verify the test lamp does not illuminate.

• If the test lamp illuminates, repair the short to ground on the circuit.

• If the test lamp does not illuminate

3. Disconnect the X1 harness connector at the K8 Blower Motor Control Module and connect the X2 harness connector at the K8 Blower Motor Control Module.

4. Verify the test lamp does not illuminate.

• If the test lamp illuminates, replace the K8 Blower Motor Control Module.

• If the test lamp does not illuminate, replace the K33 HVAC Control Module.

• If the test lamp does not illuminate

9. Turn the blower motor stepwise from low speed to high speed. The test lamp intensity should increase.

• If the test lamp does not illuminate

1. Ignition OFF, disconnect the X2 harness connector at the K8 Blower Motor Control Module, ignition ON.

2. Test for less than 0.3 V between the control circuit terminal 2 X2 and ground.

• If greater than 0.3 V, repair the short to voltage on the circuit.

• If less than 0.3 V

3. Ignition OFF.

4. Test for less than 2 ohms in the control circuit end to end.

• If greater than 2 ohms, repair the open/high resistance in the circuit.

• If less than 2 ohms

5. Replace the K8 Blower Motor Control Module.

6. Ignition ON, turn the blower motor ON and verify the test lamp illuminates.

• If the test lamp does not illuminate, replace the K33 HVAC Control Module.

• If the test lamp illuminates, all OK.

• If the test lamp intensity does not vary

1. Ignition OFF, replace the K8 Blower Motor Control Module. Keep the test lamp still connected, ignition ON.

2. Turn the blower motor stepwise from low speed to high speed. The test lamp intensity should increase.

• If the test lamp intensity does not vary, replace the K33 HVAC Control Module.

• If the test lamp intensity varies, all OK.

• If the test lamp intensity varies

10. Replace the M8 Blower Motor.

Repair Instructions

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

* Heater and Air Conditioning Control Replacement Heater and Air Conditioning Control Replacement

* Blower Motor Replacement Service and Repair

* Control Module References Control Module References for HVAC control module replacement, programming and setup

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