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.

Check the following mechanical fault sources:

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Only C68

1. Ignition ON, turn the blower motor knob on high speed then to low speed. Verify the scan tool Blower Motor Switch parameter. The reading should correspond to the selected blower step.

⇒	If not the specified value, replace the A26 HVAC Control.

Only CJ2

1. Ignition ON, press and release the switch for blower speed increase. Verify the scan tool Blower Motor Switch parameter changes between Inactive and Up.

⇒	If not the specified value, replace the A26 HVAC Control.

2. Press and release the switch for blower speed decrease. Verify the scan tool Blower Motor Switch parameter changes between Inactive and Down.

⇒	If not the specified value, replace the A26 HVAC Control.

1. Ignition OFF, disconnect the X2 harness connector at the K8 Blower Motor Control Module.
2. Test for less than 5 Ω between the K8 Blower Motor Control Module ground circuit terminal 5 (X2) and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between K8 Blower Motor Control Module the B+ circuit terminal 6 (X2) and ground.

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

4. Ignition OFF, disconnect the harness connector at the M8 Blower Motor and connect the X2 harness connector at the K8 Blower Motor Control Module.
5. Ignition ON, verify that a test lamp illuminates between the M8 Blower Motor B+ circuit terminal 1 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.

6. Connect a test lamp between the M8 Blower Motor B+ circuit terminal 1 and the M8 Blower Motor control circuit terminal 2.
7. Turn the blower motor to 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 illuminates brightly continuously, test the control circuit for a short to ground. If the circuit tests normal, replace the K8 Blower Motor Control Module and verify that the test lamp does not always illuminate brightly. If the test lamp always illuminates brightly, replace the K33 HVAC Control Module.

⇒

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 K8 Blower Motor Control Module and verify that the test lamp illuminates. If the test lamp does not illuminate, replace the K33 HVAC Control Module.

⇒	If the test lamp intensity does not vary, replace the K8 Blower Motor Control Module and verify that the intensity varies. If the test lamp intensity does not vary, replace the K33 HVAC Control Module.

8. If all circuits test normal, replace the M8 Blower Motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.