I have a 91 RS with a cooling fan problem. The previous owner cut one wire from the fan and ran it to a switch. I am trying to figure out where this wire is supposed to go. It is black in color.

 

Unless it has a red or pink stripe it goes to ground.

 

As soon as I connect it to ground the fan kicks on and stays on. Any help appreciated.

 

That's probably the reason the previous owner put in the switch. I don't know the fan circuit real well, but first I'd check for a stuck fan relay. Anyone else?

 

the previous owner probably ran a switch cuz the fan switch in the head doesn't kick in til a high temp, like 237. so, either he decided to control it himself by adding the switch, or something in the circuit itself crapped. with that said, there should be a relay on the driver side firewall that has a heavy black with red or purple stripe on it. look at the fan motor, you'll see what color it should be. the other wire is a heavy black wire, the ground. if the system was working right on its own, the switch in the head would send the signal to the relay, which would turn the fan on. 237 is pretty hot, obviously, and cooler temp switches are available if you want to put everything back to original configuration and design. i can't recall all the wires on the relay, but there are about 4, i believe. if you have only one fan, the other elay will be for the fuel pump...