a/c fan won't turn off
 

Anybody ever here of this? As soon as I turn the ignition on, the A/C fan is on full blast. I can still direct the flow (panel, floor, defrost) and temperature, but I can't control the fan speed. Even if I turn the whole climate control panel off the fan still runs. The only way to turn it off is to turn off the car.

Any ideas? 2k2 SE 6spd by the way.

I'm assuming from your description that you have the automatic climate control rather than the manual-control air conditioning.

The blower motor is driven by a FET (field effect transistor) and its gate voltage (which controls the current) is driven by the control head. Failure of either of these components could cause the fan to run at full speed continuously. My guess is that the FET is the more likely to have failed but it is only a guess, however your report that the fan runs at full speed even with the panel turned off is at least consistent with this diagnosis. Pushing the "off" button on the panel only sets the control voltage to zero - it doesn't open a physical switch, like the "off" position on the fan speed dial on the manual a/c does.

The FET is a small module bolted into the blower housing next to the motor shell, tucked up above the footwell on the passenger side. Unfortunately I cannot provide a photo.

These comments do not apply to the manually-controlled a/c. In that system the fan speed is regulated by a resistor pack. However that is much more likely to fail open than short. If this happened, the fan would not run at all, or would run only in certain switch positions.

So basically find some scrapped FET or blower and try it out (inexpensive) or just go to the dealership (more effective).

I'll check it out. Thanks.