ATC Blower Motor Speeds Incorrect

Possible Causes:

• Ground Circuit Open
• Blower Motor Control Circuit Open
• Blower Motor Control Circuit Short To Voltage
• Blower Motor Power Module
• Ground Circuit Open - Junction Block
• Body Control Module

Testing

1. Turn ignition off. Disconnect the blower motor power module harness connector. See Figure . Measure the resistance between ground and the ground circuit. If the resistance is 5 ohms or less, go to next step. If the resistance is 5 ohms or more, repair the ground circuit for an open.
2. Disconnect the BCM C2 harness connector. See Figure . Measure the resistance of the blower motor control circuit between the BCM C2 connector and the blower motor power module connector. If the resistance is 5 ohms or less, go to next step. If the resistance is 5 ohms or more, repair the blower motor control circuit for an open.
3. Turn ignition on. Measure the voltage of the blower motor control circuit. If there is any voltage present, repair the blower motor control circuit for a short to voltage. If there is no voltage present, go to next step.
4. Turn ignition off. Reconnect the blower motor power module harness connector. Connect a jumper wire between ground and the blower motor control circuit in the BCM C2 connector. Turn ignition on. If the blower motor still runs on high speed, replace the blower motor power module. See AUTOMATIC A/C-HEATER SYSTEMS - CONCORDE, INTREPID & 300M article in HVAC. If the blower motor does not run at high speed, go to next step.
5. Turn ignition on. Remove the BCM from junction block. Measure the resistance between ground and the ground circuits in the junction block BCM connector. If the resistance is 5 ohms or less for both measurements, replace the BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION. If the resistance is 5 ohms or more for both measurements, repair the ground circuit for an open to the junction block. If OK, replace the junction block. See JUNCTION BLOCK  under REMOVAL & INSTALLATION.