Okay, I think I may have pinpointed why the fan will not work on my 2004 Grand Prix. I replaced the resistor, the blower motor checks ok (I even put in another motor and it still wouldn't run), re-installed the OEM blower motor, checked the fuses again and nothing is blown there. The air conditioner compresssor still kicks on. I just don't have a fan.
That leaves the fan switch. This is integral with the whole HVAC control. The switch for the fan is like a rheostat, so there isn't a notch for 4-5 different speeds. The control for the air ducts seems to work because I can hear the module for that run. Besides, even if that didn't work, you'd think the fan would still run.
I checked again with a test light and found there is no power to the blower motor. That leaves the fan switch as a potential culprit.
I already popped the instrument panel apart and got the unit to where I could unplug it. However, if I don't know which terminals to direct my test light to, how will I know if it is defective? The Haynes manual I have primarily covers the earlier Grand Prixs and doesn't have a wiring diagram for the controller.
Does anyone have access to the schematic for this circuit, or knows which terminals to contact for a test? I think it could be defective, but I want to make sure before spending $150-plus for the replacement. I wonder if a GM service department would provide the information?
Any thoughts would be appreciated.
