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 switch assembly applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor at each speed:

* Low speed - 1 resistors
* Medium 2 speed - 2 resistors
* Medium 3 speed - 3 resistors

When the operator requests high speed, the blower switch applies voltage to the high speed blower control circuit. directly to the blower motor.

Reference Information
Schematic Reference

HVAC Schematics (without WHB) (HVAC Schematics (without WHB))HVAC Schematics (with WHB) (HVAC Schematics (with WHB))
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Air Delivery 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) for scan tool information

Circuit/System Verification

1. Place the blower switch in the High speed position. The blower motor should operate at High speed.

• If the blower motor does not function properly in the High speed position, refer to High Speed Blower Malfunction.

2. Place the blower switch in Low, Medium 1 and Medium 2 speed positions. The blower motor should operate in each speed position.

• If the blower motor does not function properly in each speed position, refer to Blower Malfunction.

Circuit/System Testing

Blower Malfunction
1. Ignition OFF, disconnect the harness connector at the blower motor resistor.
2. Ignition ON, while cycling the blower switch between each speed position, verify a test lamp illuminates between the appropriate control circuit terminal listed below and ground:

* Low - Terminal 1
* Medium - Terminal 3
* Medium 2 - Terminal 4

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the blower switch.

3. Reconnect the HVAC blower resistor and disconnect the HVAC blower motor, verify a test lamp illuminates between the control circuit terminal 2 and ground when switched to each speed position:

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

Repair Instructions

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

* Blower Motor Switch Replacement (Service and Repair)
* Blower Motor Replacement (Service and Repair)
* Blower Motor Resistor Replacement (Service and Repair)