The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive and ground circuits enable the control module to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the blower motor speed control module in order to command the blower motor speed. The module supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the harness connector at the blower motor control module.
2. Test for less than 1.0 ohm between the ground circuit terminal C 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 A 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 B and the B+ circuit terminal A.
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 volts while changing between the commanded states, test the control circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

⇒	If voltage remains less than 1.0 volt 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 HVAC control module.

⇒	If voltage is between 1.0 and 11.5 volts but does not increase when changing between the commanded states, replace the HVAC control module.

6. Ignition OFF, connect the harness connector at the blower motor control module. Disconnect the harness connector at the blower motor.
7. Ignition ON, verify that a test lamp illuminates between the control terminal A and ground.

⇒	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 blower motor control module.

8. Connect a test lamp between the control circuit terminal A and the control circuit terminal B.
9. Turn the blower motor ON high speed then to low speed. The test lamp intensity should be bright when at high speed and very dim or off when the blower is on low speed.

⇒	If the test lamp remains at full intensity at all times, test the control circuit terminal B for a short to ground. If the circuit tests normal, replace the blower motor control module.

⇒	If the test lamp remains dim or off at all times, test the control circuit terminal B for a short to voltage or an open/high resistance. If the circuit tests normal, replace the blower motor control module.

10. If all circuits test normal, test or replace the blower motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.