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Blower Motor Malfunction



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

Blower Motor Control Module

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 pulse width modulation (PWM) signal to the blower motor speed control module in order to command the blower motor speed. The module supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the blower motor control module connector X2.
2. Test for less than 1.0 ohm of resistance between the ground circuit connector X2 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 of the blower motor speed control module supply voltage terminal connector X2 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 15-amp) in the instrument panel (IP) BEC is open, test all components connected to the B+ circuit and replace as necessary.

4. Connect a test lamp between the blower motor speed control circuit connector X1 terminal 3 and the blower motor supply voltage circuit connector X2 terminal 6 of the blower motor control module.
5. Turn the blower motor ON and then OFF. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the HVAC control module.
• If the test lamp is always OFF, test the speed control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

6. Ignition OFF, connect the harness connector at the blower motor control module.
7. Disconnect the harness connector at the blower motor terminal A.
8. Ignition ON, verify that a test lamp illuminates between the blower motor supply voltage circuit terminal 6 of the blower motor control module and ground.

• If the test lamp does not illuminate, test the blower motor supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor control module.

9. Connect a test lamp between the blower motor supply voltage circuit terminal 6 and the blower motor ground circuit terminal 5 of the blower motor control module.
10. Turn the blower motor ON high speed then to low speed. The test lamp intensity should be bright when ON high speed and very dim or out when the blower is on low speed.

• If the test lamp intensity is not correct, test the blower motor ground circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the blower motor control module.

11. If all circuits test normal, replace the blower motor.

Repair Instructions

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

* Blower Motor Control Module Replacement
* Blower Motor Replacement
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