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, 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.
Diagnostic Aids
Prior to motor replacement connect a direct independent B+ and ground to verify operation.
Inspect the motor shaft for rust or other foreign material which may prohibit proper motor operation.
If the motor operates properly please reinstall it, check for PIs or TSBs, and refer to Testing for Intermittent Conditions and Poor Connections in the Electrical Information Reference section of this document.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Automatic
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
* Air Delivery Description and Operation Air Delivery
* Air Temperature Description and Operation Air Temperature
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, and all vehicle systems OFF. Disconnect the X2 harness connector at the blower motor control module. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the ground circuit terminal 5 and ground.
• If 5 ohms or greater
1. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Ignition ON
4. Verify a test lamp illuminates between the B+ circuit terminal 6 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, replace the blower motor control module.
• If the test lamp illuminates
5. Connect a DMM between the control circuit terminal 3 and ground.
6. Verify the resistance value is between.1 Mohms and 3.3 Mohms and there is a noticeable change when moving between the commanded fan speeds.
• If not between.1 Mohms and 3.3 Mohms or there is no noticeable change
1. Ignition OFF, disconnect the X3 harness connector at the HVAC control module, Ignition ON.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Ignition OFF
4. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
5. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the HVAC control module.
• If between.1 Mohms and 3.3 Mohms and there is a noticeable change
7. Ignition OFF, connect the X2 harness connector at the blower motor control module, and disconnect the harness connector at the blower motor, ignition ON and blower ON.
8. Verify a test lamp illuminates between the B+ circuit terminal A and ground.
• If the test lamp does not illuminate
1. 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
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 blower motor control module.
• If the test lamp illuminates
9. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.
10. Verify the test lamp turns ON and OFF when moving the blower switch between the ON and OFF positions.
• If the test lamp is always OFF
1. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
2. Test for less than 2 ohms in the control circuit from end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the blower motor control module.
• If the test lamp is always ON
1. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the blower motor control module.
• If the test lamp turns ON and OFF
11. 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 setup, programming, and setup