My single cooling fan would only come on when the a/c was on- now it won't come on at all, regardless. The relay has been replaced, but I don't know where the fan switch is...or is there some other issue that you can think of that would cause the fan to run with the a/c on but not without and now won't run at all?

 

Have you checked to see if the fan is getting current? Maybe a bad motor. I'd start there and work back.