I have a '92 RS with a V6 and my cooling fan doesn't come on when the temp goes up. It will come on when I turn on my AC. Another problem that may be related to it is that my temp guage will sometimes fluxuate rapidly. Most allways when the engine is cold. It'll be started up for about 30sec to a minute and the guage will go quickly almost to the red. And then it will come back down to about 250 or so after a couple of minutes and back and forth with that happening. I know it's not actually hot, since I just started it up and my heater is still blowing cold. It seems like when it's warmed up, the guage is fuctioning properly. If I sit in traffic for a long while, it'll go up about halfway between the half mark and max. And the fan never comes on. I know you're supposed to turn off the AC if you're overheating, but ironicly with mine, I turn it on and the temp goes down cause that's the only way I can get my fan to turn on. Interstate driving and no traffic while I'm in town driving I have no temp problems with. My normal temp seems to be about 150 to 160 as long as the guage is reading properly.
I've checked the fan fuse under the dash and it was good.
Could a relay be bad? If so, where is it located? Could it be my temp sensor needs replaced? What should be my first route?
Thanks.

 

first, your temp gauge is bad. fixing this might cure the fan on/off timing, or you can wire the fan to come on when the power is turned on-that way it is always on.