I have a 91 RS 305 tbi. I dont know what the cooling fan switch on top of the thermostat housing looks like. I have a circular one with one wire coming out of it. When I go to a part store to get a new it looks different. It has two wires coming out, a yellow, and a black one. I dont know if mine has the wrong one it.

 

The yellow and black wire sound like the coolant temp sensor that sends information to the ECM. There should be another for the guage on your dash. I'm talking from the experience with my TPI 350 here though. The fan switch should be in the passenger side head between the two middle plugs.

 

So what is the switch that is located on the thermostat housing and what do the two wires go to? I need to get this fixed because I grounded my only fan so its on all the time. I do not want it to burn out.

 

I'll check out my Chilton's and see if I can give you a definate answer. Like I said, I'm much more familiar with TPI. It does however, sound to me like the coolant temp sensor. On my car, those two wires connect into a harness on the passenger side of the engine.

Were you having problems with the fan turning off and that's why you grounded it so it would constantly run? If that's why, I believe you've just found your problem. The fan should be controlled by the ECM. On the sensor you're describing, that yellow wire goes to the ECM telling it when to turn on the fan. The black wire grounds out.

 

My fan would not turn on unless I had my a/c on so I grounded it so it runs all the time. I need to know what that switch on the thermostat housing looks like. I think I have the wrong one on it.

 

You could take the part that you think is broken out and bring it to the parts store with you. Or you could look on it and it might have a GM part number on it, and then you could call the dealership or call a parts store and give them the GM part number to cross reference.

 

Its not a gm part, I Just need a picture of someone elses TBI 305 and I would be able to tell if I have the wrong switch on the thermostat housing or not. Because I took it in a long time ago in virginia and I think they put a quick fix on it and put the wrong switch there instead of the one that is supposed to go. And I looked in the Haynes book and there is no picture so I cant tell. I have not looked in a chilton yet.