Vehicle Description: 2004 Honda Pilot 3.5L
Mileage: 76,975
Customer Concern: No A/C compressor clutch. The scan tool says A/C off and A/C switch off. There is no air out of the front vents, but the blower motor operates and changes speeds with the front switch.
Tests/Procedures:
1. Ground the blue/red wire at the front blower power transistor and verify the blower motor runs on high speed.
2. Verify the front blower power transistor ground is good on the black wire — look for 0.05 volts or less to be OK.
3. Check the control signal from the climate control unit to the front blower power transistor on the orange/black wire. Look for voltage to be present when the front blower motor switch is turned on.
4. Unplug the front blower power transistor connector and remove or cut the orange/black wire from the front blower power transistor connector, then plug the front blower power transistor back in and use a powered up test light on the terminal of the front blower power transistor that the orange/black wire would normally go to and see if the front blower motor will operate then.
5. Check the blower feedback (ground side of the blower motor back through the front blower power transistor) back to the climate control unit on the second blue/black wire in the connector.
Potential Causes: Front blower power transistor; this was the confirmed fix. It turned out to be the rear blower motor that was running and not the front blower motor.
Tech Tips: It is not uncommon for a technician to believe the front blower motor is working when it is actually the rear blower motor that is working. This vehicle has two blower motors. The front blower motor is under the right side of the dash near the right kick panel. The rear blower motor is located near the floor in the center console below the radio and heater controls. The A/C compressor will not work if the front blower motor is not operating.
The front blower power transistor (located near the front blower motor) controls the ground for the front blower motor. The front blower power transistor is controlled by the climate control unit. The front blower power transistor has blower feedback to the climate control unit for the climate control unit to know if the front blower motor is being grounded to turn it on.
Source: From the Identifix Hotline Archives