Auxiliary Blower Motor Malfunction

/ 9-5 (9650) / 2011 / 8. Body / Automatic Climate Control, ACC / Fault diagnosis, fault symptoms / Auxiliary 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
Rear Blower Motor Control Module B+	B0208 06	B0208 06	-	-
Rear Blower Motor B+	1	1	-	-
Rear Blower Motor Control Module Control	B0208 06	B0208 06	B0208 01	-
Rear Blower Motor Control	2	1	1	-
Rear Blower Motor Control Module Ground	-	1	-	-
1. Rear Blower Motor Inoperative 2. Rear Blower Motor Always ON

Circuit/System Description

The blower motor control module - auxiliary is an interface between the HVAC control module and the blower motor - auxiliary. The Blower Motor Speed Control from the HVAC Control Module, battery positive and ground circuits enable the Blower Motor Control Module - Auxiliary to operate. The HVAC Control Module provides a Pulse Width Modulation (PWM) signal to the Blower Motor Control Module - Auxiliary in order to command the blower motor speed. The blower motor control module - auxiliary 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

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC 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, press and release the blower speed increase switch. Verify the scan tool Auxiliary Blower Motor Switch parameter. The reading should correspond to the selected blower step.

2.	If not the specified value, replace the A21 Radio/HVAC Controls - Auxiliary.

3.	Press and release the blower speed decrease switch. Verify the scan tool Auxiliary Blower Motor Switch parameter. The reading should correspond to the selected blower step.

4.	If not the specified value, replace the A21 Radio/HVAC Controls - Auxiliary.

Circuit/System Testing

1.	Ignition OFF, disconnect the X1 harness connector at the K8A Blower Motor Control Module - Auxiliary.

2.	Verify that a test lamp illuminates between the K8A Blower Motor Control Module - Auxiliary ground circuit terminal 4 X1 and B+.

3.	If the test lamp does not illuminate, test the ground circuit for an open circuit/high resistance.

4.	Ignition ON, verify that a test lamp illuminates between the K8A Blower Motor Control Module - Auxiliary B+ circuit terminal 2 X1 and ground.

5.	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

6.	Ignition OFF, disconnect the harness connector at the M8B Blower Motor - Auxiliary and connect the X1 harness connector at the K8A Blower Motor Control Module - Auxiliary.

7.	Ignition ON, verify that a test lamp illuminates between the M8B Blower Motor - Auxiliary B+ circuit terminal B and ground.

8.	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 K8A Blower Motor Control Module - Auxiliary.

9.	Connect a test lamp between the M8B Blower Motor - Auxiliary B+ circuit terminal B and the M8B Blower Motor - Auxiliary control circuit terminal A.

10.	Turn the blower motor OFF. Verify the test lamp does not illuminate.

11.	If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K8A Blower Motor Control Module - Auxiliary and verify that the test lamp does not always illuminate. If the test lamp always illuminates, replace the K33 HVAC Control Module.

12.	Turn the blower motor stepwise from low speed then to high speed. The test lamp intensity should increase.

13.

If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K8A Blower Motor Control Module - Auxiliary and verify that the test lamp illuminates. If the test lamp does not illuminate, replace the K33 HVAC Control Module.

14.	If the test lamp intensity does not vary, replace the K8A Blower Motor Control Module - Auxiliary and verify that the intensity varies. If the test lamp intensity does not vary, replace the K33 HVAC Control Module.

15.	If all circuits test normal, replace the M8B Blower Motor - Auxiliary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Auxiliary Heater and Air Conditioning Control Module Replacement

•	Heater and Air Conditioning and Radio Control Module Replacement

•	Control Module References for HVAC control module replacement, setup, and programming

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