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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 height 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 ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning)

Circuit/System Verification

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. Switch the climate control system to the manual setting. Turn the fan speed control knob from the lowest to highest setting. The blower motor speed should change between commanded states.
3. Turn the blower speed control knob to the "O" position. The blower motor should turn OFF.

Circuit/System Testing

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

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

3. 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.

4. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module.
5. Ignition ON, test for less than 0.3 V between the control circuit terminal 3 X1 at the K8 Blower Motor Control Module harness connector and ground.

• If greater than the specified value, test the control circuit for a short to voltage.

6. Ignition OFF, test for infinite resistance between the control circuit terminal 3 X1 at the K8 Blower Motor Control Module harness connector and ground.

• If less than the specified value, test the control circuit for a short to ground.

7. Test for less than 5 ohm between the K33 HVAC Control Module control circuit terminal 15 X2 and control circuit terminal 3 X1 at the K8 Blower Motor Control Module harness connector.

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

8. Ignition OFF, connect the X1 harness connector at the K8 Blower Motor Control Module and disconnect the harness connector at the M8 Blower Motor.
9. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B 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.

10. Ignition OFF, connect the X2 harness connector at the K33 HVAC Control Module.
11. Connect a test lamp between the M8 Blower Motor B+ circuit terminal B and the M8 Blower Motor control circuit terminal A.
12. Turn the blower motor on high speed then to low speed. The test lamp intensity should be bright when in high speed and very dim or off when the blower is on low speed.

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

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

Repair Instructions

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

* Blower Motor Control Module Replacement (Service and Repair)
* Blower Motor Replacement (Blower Motor Replacement)
* Heater and Air Conditioning Control Replacement (Heater and Air Conditioning Control Replacement)
* Control Module References (Programming and Relearning)

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