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.

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, battery positive and ground circuits enable the control module to operate. The HVAC control module provides a variable voltage to the blower motor control module to request the selected blower speed. The blower motor control module provides a pulse width modulation (PWM) signal to the blower motor in order to control the blower motor speed. The module supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Reference Information

Schematic Reference

HVAC Schematics HVAC - Automatic

Connector End View Reference

Component Connector End Views Connector End Views By Name

Description and Operation

* Air Temperature Description and Operation Air Temperature

* Air Delivery Description and Operation Air Delivery

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 OFF, disconnect the X2 harness connector at the blower motor control module.

2. Test for less than 1.0 ohms between the ground circuit terminal 5 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 the B+ circuit terminal 6 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 and the B+ circuit fuse (HVAC BLWR 40-amp) in the underhood fuse block is open, test all components connected to the B+ circuit and replace as necessary.

4. Connect the X2 harness connector at the blower motor control module and connect DMM between the control circuit terminal 3 and ground.

5. Cycle the blower motor from OFF to HIGH. The voltage should decrease while changing between the commanded states.

• If voltage remains greater than 11.5 V while changing between the commanded states, test the control circuit for a short to voltage. If the circuit test normal, replace the HVAC control module.

• If voltage remains less than 1.0 V while changing between the commanded states, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

• If voltage is between 1.0-11.5 V and does not decrease when changing between the commanded states, replace the HVAC control module.

6. Ignition OFF, connect the X2 harness connector at the blower motor control module. Disconnect the harness connector at the blower motor.

7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A 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 blower motor control module.

8. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.

9. 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 blower motor control module.

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

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Blower Motor Control Module Replacement Blower Motor Control Module Replacement

* Blower Motor Replacement Service and Repair

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