Hi
I have an 07 4 cyl. and the heater/blower fan is coming on even though the car is off and the heater fan control is in the off position. I have tried leaving the fan on low and the temperature control above the coldest setting before turning the car off, and no luck. Blower came on during night and drained battery. Dealer checked blower and wires to it, but found nothing.

Any suggestions?
Greg

 

Unlike older blower motor designs, this motor setup includes a power transistor that responds to pulses from the A/C amplifier. The longer or shorter the pulse, the faster or slower the blower speed.

The motor control has battery power and a chassis ground. The A/C amplifier sends pluses to activate motor.

Try disconnecting the red wire from the motor control that goes to the A/C amp. If blower still comes with ign switch off the problem is the blower control on motor.

 

Thanks for the response. I picked up the car from the dealership yesterday and so far so good. They checked the blower and surrounding area as well as charged the battery which was completely drained. I'm hoping there was a lose connection or something like that, but that's just wishful thinking. I will be following your suggestions as soon as the problem shows up again. I'll keep you posted.

 

The problem started again. I just went out and found the fan running. Without starting the car, I gave the bottom of the blower a thump and it stopped. Any suggestion on the next step? I haven't disconnected any wires yet. I found a picture online showing where the AC amplifier is located, but is the blower motor control directly on the blower?

 

The electronic blower motor on/off/speed control is on the blower unit which always has access to DC power.

The A/C amp as wired should power off with ign key. The A/C amp controls the motor control. It is what should be signalling the motor control to turn on/off and RPM setting.

You can isolate the A/C amp from motor control by disconnecting the red wire at the motor. If motor still turns on, problem must be in the motor control.

If/when you again find the motor running, unplug motor harness. If motor still runs then check motor, if it stops then A/C amp, and; amp is powered by a relay which also control wipers and washer. If fan running determine if these items also operate, if so then check IG1 relay.

 

Update. Yesterday, for the first time the fan came on while driving. I immediately pulled over, left the car running and disconnected the harness pin connection (not blower end) containing the red wire that leads to the blower. The fan kept running and only stopped when I re-installed the connector. I disconnected the red wire from the blower and when I checked this morning the fan was running on it's own again. As you suggested, it is likely the blower so I just installed a replacement and I'll update you in a few days, but here's hoping.

Thanks again for your expert advise. I would have been completely lost without it.

Greg

 

Good work. Keep us informed.

 

The new blower seems to have fixed the problem. It's been several days and no issues.

Thanks again

Greg

 

Great, good job. Thanks for posting back.