The radiator cooling fan in my 04 cavalier is not working. I replaced the entire cooling fan assembly last summer and the cooling fan worked fine. This summer it decided to stop working. The relay is good and the wires look good. I haven't checked my coolant temperature sensor yet. Also the thermostat is new, it was replaced last summer when I replaced the cooling fan assembly. When i'm driving on the highway with the AC on the engine temperature starts to rise slightly and when I stop at a red light the AC starts blowing hot, but as soon as I start moving again it blows cold. It has me stumped. If anyone could give me some advice it would be greatly appreciated.

I also heard that the cooling fan could be wired to a switch so that it could be turned on that way. That would be good also.

I disconnected the coolant temperature sensor while the car was running and the fan didn't cut on.