95 Grand Prix cooling fan problem.

1995 GP SE 3.1, fan number 2 will not activate. Checked and swapped relays, no change. Checked fuses, all ok. Checked fan motor, ok. checked with car running, AC on full, no 2nd fan. Fan number 1 works fine. Any thoughts?

I think 1 fan turns on at a certain temp, and the other fan turns on when the temp is higher. I am not sure what the temps are though.

As a test you can unplug the coolant temp sensor and then start the car to see if both will run. If the PCM loses the temperature signal, it commands both fans on to keep the motor from overheating.

If only one fan runs, I would suspect maybe the fan driver circuit internal to the PCM is at fault.

Disconnected temp sensor. fired it up, both fans came on. Any other tests you can think of or should I start looking for a PCM?

Because both fans came on, wouldn't that lend itself more to a bad temp sensor?

good call, does the temp guage work?

But I think your car might just not be getting warm enough to kick the second fan on.

Why are you worried? Did your car overheat?

I agree with Tim. The second fan will only come on if engine temp exceeds 235 degrees. It should come on when the AC is set to max and ambient outside temps are above a certain temp (sorry, I don't know what that exact temp is, but I believe it's above 80), but it won't if the AC is just on normal settings or outside temps are below the PCM programming threshold.

All is well, just didn't understand the system that well. Thanks for your help guys.

No problems!

Come back again with any of your questions!