I have an 89 RS with the 305 TBI. My cooling fan is not working. I replace the relay, the coolant fan switch and my thermostat. The fan runs, i have it hooked up to a toggle switch, through my relayin my car right now. So i control when it goes on and off. The ? i have is there are 2 wires running from my coolant fan switch, a Dark green or black not sure cause its so old, and what look to be a white or yellow once angain not sure cause the wiring is old. I have the wiring diagram for my cooling system and it dosent show a white/yellow wire. The wire itself runs under my block somewhere then just kind of disappers, Its connected to something cause we cant pull it out. Does any one have an idea where that wire is running to or what the point of it is.

 

i had the same problem if u trace the wires with a volt meter you'll notice that the voltage goes into the computer but never returns out...ultimatly everything i tried didn't work on fixing it but if you go to a local parts store and ask for a seperate setup they have a thing u put in your upper radiator hose and hook to the fan and that will turn you fan on and off and mine is fully adjustable so i can go from 150 to like 230 degrees it also has a seperate spot u can hook up a back up switch to so u can turn it when ever u want....might be a good idea to check into that cause my god father ran into the same problem with his

 

i have power everywhere. Except in the white/gray wire coming off my fan switch sensor. I dont know nor can i locate where that wire goes.

 

Not sure of the wiring schematics, but the same thing happened in my '91, and the jackasses that I took the car to couldn't figure it out either, so they rigged up a switch like you said. I finally got around to taking it to my usual mechanic, and he said that there is a sensor on eachhead; one goes to the fan relay switch and the other is for the temp gauge. Is it possible that the wire is going to the other sensor on the other side of the engine? Turned out that both of my sensors were bad, so now they've been replaced and everything is running great and very cool!