When I purchased my '90 it had already had a fan switch installed. I checked a diagram of another user who had done the same and it was installed properly. It always worked until today. When I flip the switch nothing happens. I checked the circuit and it is getting no power. I have went over all the wiring and can't find a problem. My guess is a bad relay or fan motor. Does the fact that there is no power in the circuit narrow it down?