Okay... As many of you know I am having issues with my 96 SE'* fans not coming on unless the A/C is on. What I am trying to understand is how they operate. I have read numerous posts on cooling fan issues but none seemed to get into how they work.

There are two fans. A large and a small.
1. Do they always come on at the same time?
2. I see in the diagram they are wired to the TPS. Why? Is that a shared ground?
3. What dictates the high and low speed? Climate control position, coolant temperature and vehicle speed?
4. The two resistors on the large fan are to cut the voltage to allow the fans to run on low speed?
5. Would I be correct to assume that everything shown on the diagram is part of the circuit?

Side note: I changed the ECT sensor and both fan relays.

Thanks guys,
Dean

*** Moved from Chat - Kevin ***

Sorry about posting in the wrong area. I thought it was a generalized question affecting more than just 92-99. Actually should this go in electrical?
Dean

The fans turn on by the ECT. They will turn on earlier if the AC is on, and will turn off if the car is moving, that'* why the TPS is involved.

I'm not sure if this will help you or not but, on my 89 Bonneville I had trouble with the cooling fans. They woould not come on at any time. The A/C was not working at the time (low on freon). I took it to my mechanic and he disconnected the wire to the A/c near the evporator and jumped teh plug with a bent paperclip. I didn't ask any more questions, the fan worked fine and I drove it another year or two without A/c and teh paperclip in place.