I have a 2003 Deville that has an odd problem: The fan for the AC usually will not come on until I hit a bump with the left wheels at about 10-15 MPH. Once it is running, it doesn't go off if I hit another bump, so I think it's probably some sort of starter relay issue. If I turn the fan down (or if the climate control turns it down) below about 1/4, it goes off and will not come back on until I hit another bump.
Automobile(s): 58 Coupe Deville, 77 Coupe deville, 90 Deville
Re: Weird AC fan issue
Sounds like a loose connection to me, that may be hard to find. You could start by checking (wiggle the wires a bit) the connections at the blower motor. If you can find the relays using your owners manual try tapping lightly on them and see if that makes the motor run. If it does replace the relay. There may very well be something that others more familiar with this car could suggest, hopefully they will speak up if so.
The AutoZone free computer check didn't find a problem, so I took it to the dealer, which charged me $95 to hook up their sensor and read that the blower motor had a short. They offered to replace it - for $675. I declined that offer and bought an aftermarket blower for $60, which took ten minutes to replace. Love my Cad, but not so happy with the Cad dealer.