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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 - Automatic)
Connector End View Reference

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

Automatic HVAC Description and Operation (HVAC - Automatic)
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 (Programming and Relearning) 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 not the specified value, replace the A26 HVAC Control.

2. Ignition OFF, disconnect the X1 harness connector at the K8 Blower Motor Control Module.
3. Test for less than 5 ohm between the K8 Blower Motor Control Module ground circuit terminal 5 X1 and ground.

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

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, test the B+ circuit for a short to ground or an open/high resistance.

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.
6. Ignition ON, verify that a test lamp illuminates between the M8 Blower Motor B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K8 Blower Motor Control Module.

7. Connect a test lamp between the M8 Blower Motor B+ circuit terminal 1 and the M8 Blower Motor control circuit terminal 2.
8. Turn the blower motor OFF. Verify the test lamp does not illuminate.

• If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K8 Blower Motor Control Module and verify that the test lamp does not always illuminate. If the test lamp always illuminates, replace the K33 HVAC Control Module.

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, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K8 Blower Motor Control Module and verify that the test lamp illuminates. If the test lamp does not illuminate, replace the K33 HVAC Control Module.
• If the test lamp intensity does not vary, replace the K8 Blower Motor Control Module and verify that the intensity varies. If the test lamp intensity does not vary, replace the K33 HVAC Control Module.

10. If all circuits test normal, replace the M8 Blower Motor.

Repair Instructions

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

* Heater and Blower and Air Conditioning Control Module Replacement (Left Hand Drive) (HVAC - Automatic)
* Heater and Air Conditioning Control Replacement (HVAC - Automatic)
* Blower Motor Replacement (Left Hand Drive) (Service and Repair)
* Control Module References (Programming and Relearning) for HVAC control module replacement, setup, and programming

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