GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Malibu 🢒 HVAC 🢒 HVAC - Manual 🢒 Blower Motor Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • 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

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

HVAC Module B+

1

1

--

--

Run Relay B+

1

1

--

--

HVAC Module Ignition

1

1

--

--

HVAC BLOWER HIGH Relay Ignition

2

2

--

--

HVAC BLOWER HIGH Relay Control

1

1

6

--

Blower Motor Control

1

1

6

--

Blower Motor Medium 2 Control

1

3

6

--

Blower Motor Medium 1 Control

1

4

6

--

Blower Motor Low Speed Control

1

5

6

--

Blower Motor Ground

--

1

--

--

HVAC Module Ground

--

1

--

--

1. Blower Motor Inoperative - All Speeds

2. Blower Motor Inoperative - High

3. Blower Motor Inoperative - Medium 2

4. Blower Motor Inoperative - Medium 1

5. Blower Motor Inoperative - Low

6. Blower Motor Always ON

Circuit/System Description

The HVAC control 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 - 4 resistors
    • Medium 2 speed - 3 resistors
    • Medium 1 speed - 2 resistors

When the operator requests high speed, the HVAC control assembly applies voltage to the high speed blower relay control circuit. When the relay contacts close, voltage is applied directly to the blower motor.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Air Temperature Description and Operation
    •  Air Delivery Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, verify the RUN relay turns ON.
    2. ⇒If the RUN relay does not turn ON, refer to the RUN Relay Malfunction.
  2. Place the blower switch in the High speed position. The blower motor should operate at High speed.
    3. ⇒If the blower motor does not function properly in the High speed position, refer to High Speed Blower Malfunction.
  3. Place the blower switch in Low, Medium 1 and Medium 2 speed positions. The blower motor should operate in each speed position.
    4. ⇒If the blower motor does not function properly in each speed position, refer to Blower Malfunction.

Circuit/System Testing

RUN Relay Malfunction

  1. Ignition OFF, disconnect the RUN relay.
  2. Ignition ON, verify the test lamp illuminates between the B+ circuit terminal 30 and ground.
    3. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  3. Verify the test lamp illuminates between the B+ circuit terminal 85 and ground.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, install a test lamp between the B+ circuit terminal 85 and control circuit terminal 86.
  5. Ignition ON, verify the test lamp illuminates.
    6. ⇒If the test lamp does not illuminate, replace the BCM.
  6. If all circuits test normal, test or replace the RUN relay.

High Speed Blower Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the HVAC control module.
  2. Test for less than 5 ohms between the ground circuit terminal A12 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A1 and ground.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for short to ground or an open/high resistance.
  4. Verify a test lamp illuminates between the ignition circuit terminal A2 and ground.
    5. ⇒If the test lamp does not illuminate, test the ignition circuit for short to ground or an open/high resistance. If the circuit tests normal, test or replace the RUN relay.
  5. Ignition OFF, disconnect the X2 harness connector at the HVAC control module.
  6. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal G and ground.
    7. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  7. Connect the harness connectors at the HVAC control module. Disconnect the HVAC BLOWER HIGH relay.
  8. Ignition OFF, test for less than 5 ohms between the relay coil ground circuit and ground.
    9. ⇒If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  9. Ignition ON, verify a test lamp illuminates between the relay switch ignition circuit terminal and ground.
    10. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  10. Blower switch on HIGH, verify a test lamp illuminates between the relay coil control circuit and ground.
    11. ⇒If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  11. Ignition OFF, connect the HVAC BLOWER HIGH relay. Disconnect the harness connector at the blower motor.
  12. Test for less than 5 ohms between the ground circuit terminal A and ground.
    13. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  13. Ignition ON, blower switch on HIGH, verify a test lamp illuminates between the control circuit terminal B and ground.
    14. ⇒If the circuit tests normal, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the HVAC BLOWER HIGH relay.
  14. If all circuits test normal, test or replace the blower motor.

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:
    3. • Low - Terminal D
    • Medium 2 - Terminal A
    • Medium 1 - Terminal B
    ⇒If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the HVAC control module.
  3. Install a 20A fused jumper wire between B+ and the control circuit terminal C. Verify the blower motor turns ON.
    4. ⇒If the blower motor does not turn ON, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal test or replace the HVAC BLOWER HIGH relay.
  4. If all circuits test normal, test or replace the blower motor resistor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Blower Motor Resistor Replacement
    •  Blower Motor Replacement
    •  HVAC Control Module Replacement