• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
B+ | -- | 1 | -- | -- |
Blower Motor Speed Control | 1 | 1 | 2 | -- |
Blower Motor Control (+) | -- | 1 | -- | -- |
Blower Motor Control (-) | 2 | 1 | -- | -- |
Ground | -- | 1 | -- | -- |
1. Blower Motor Inoperative 2. Unable to Change Blower Speed |
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.
Control Module References for scan tool information
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
⇒ | 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. |
⇒ | 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. |
⇒ | 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. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for HVAC control module replacement, setup, and programming |