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 (C68) (HVAC Schematics (C68))HVAC Schematics (CJ2) (HVAC Schematics (CJ2))
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Automatic HVAC Description and Operation (Description and Operation)
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 Verification
1. Ignition ON, press and release the POWER switch. Verify the scan tool Front HVAC System Status parameter changes between Off and On.
• If not the specified value, replace the A20 Radio/HVAC Controls.
2. Ignition ON, press and release the blower speed increase switch. Verify the scan tool Blower Motor Switch parameter changes between Inactive and Up.
• If not the specified value, replace the A20 Radio/HVAC Controls.
3. Press and release the blower speed decrease switch. Verify the scan tool Blower Motor Switch parameter changes between Inactive and Down.
• If not the specified value, replace the A20 Radio/HVAC Controls.
4. Press and release the AUTO Switch. Verify the scan tool Auto HVAC Button parameter changes between Active and Inactive.
• If not the specified value, replace the A20 Radio/HVAC Controls.
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 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. Connect a DMM between the control circuit terminal 3 X1 and ground.
5. Cycle the blower motor from OFF to HIGH. The voltage should increase 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 K33 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 K33 HVAC Control Module.
• If voltage is between 1.0-11.5 V and does not increase when changing between the commanded states, replace the K33 HVAC Control Module.
6. Ignition OFF, connect the X1 harness connector at the K8 Blower Motor Control Module and disconnect the harness connector at the M8 Blower Motor.
7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 2 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.
8. Connect a test lamp between the B+ circuit terminal 2 and the control circuit terminal 1.
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 K8 Blower Motor 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 (Service and Repair)
* Blower Motor Replacement (Service and Repair)
* Radio Control Assembly Replacement (Radio Control Assembly Replacement)
* Control Module References (Programming and Relearning)for HVAC Control Module replacement, setup, and programming