Manual A/C Blower Motor Inoperative

Possible Causes:

• Junction Block Fuse No. 23
• Fused Ignition Switch Output CKT Shorted To Ground
• Blower Motor - Short To Ground
• Fused Ignition Switch Output Circuit Open To Resistor
• Fused Ignition Switch Output Circuit Open To Motor
• Blower Motor Open
• Blower Motor Inoperative
• Ground Circuit Open
• Head - Motor Driver Open
• Blower Motor Driver Circuit Open
• Resistor - Open Hi Blower Motor Driver

Testing

1. Remove and inspect fuse No. 23 from junction block. See Figure . If the fuse is open, go to next step. If the fuse is not open, go to step  4 .
2. Turn ignition off. Replace fuse No. 23 in the junction block. Turn ignition on. Turn the blower on and operate it in all speeds and modes. If the blower motor operates properly without blowing the fuse, check the fused ignition switch output circuit for an intermittent short to ground. If the blower motor does not operate properly without blowing the fuse, go to next step.
3. Turn ignition off. Disconnect the blower motor 2-way harness connector. Measure the resistance between ground and the fused ignition switch output circuit. If the resistance is 5 ohms or less, check the blower motor resistor block for resistance to ground. If OK, repair the fused ignition switch output circuit for a short to ground and replace the fuse. If the resistance is 5 ohms or more, replace the blower motor and fuse. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC.
4. Ensure junction block fuse No. 23 is installed before proceeding. Turn the blower motor switch off. Disconnect the blower motor resistor block harness connector. Turn ignition on. Measure the voltage of the fused ignition switch output circuit. If the voltage is 10 volts or more, go to next step. If the voltage is 10 volts or less, repair the fused ignition switch output circuit.
5. Reconnect the blower motor resistor block harness connector. Turn ignition on. While backprobing, measure the voltage of the fused ignition switch output circuit at the blower motor 2-way connector. If the voltage is 10 volts or more, go to next step. If the voltage is 10 volts or less, replace the blower motor resistor block. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC.
6. Turn the blower motor switch off. Turn ignition on. While backprobing, measure the voltage of the blower motor driver circuit at the blower motor 2-way connector. If the voltage is 10 volts or more, go to next step. If the voltage is 10 volts or less, replace the blower motor. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC.
7. Backprobe a jumper wire between ground and the blower motor driver circuit at the blower motor 2-way connector. If the blower motor ran at high speed, go to next step. If the blower motor did not run on high speed, replace the blower motor. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC.
8. Disconnect the manual temperature control head C2 harness connector. See Figure . Connect a jumper wire between the high blower motor driver and ground in the control head C2 connector. Turn the ignition on. If the blower motor ran at high speed, go to next step. If the blower motor did not run at high speed, go to step  10 .
9. Turn ignition off. Measure the resistance between ground and the ground circuit. If the resistance is 5 ohms or less, replace the control head. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC. If the resistance is 5 ohms or more, repair the ground circuit for an open.
10. Disconnect the blower motor resistor block harness connector. See Figure . Measure the resistance of the high blower motor driver circuit between the control head C2 connector and the blower motor resistor block connector. If the resistance is 5 ohms or less, replace the blower motor resistor block. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC. If the resistance is 5 ohms or more, repair the high blower motor driver circuit for an open.