I have a 2003 pontiac that my fans don’t kick in to high speed, so when I am in traffic the heat gauge keeps climbing. I believe its a fan sensor…does anyone know where that is located on my car.

Thanks for your help

A Hatnes manual from the local parts store will show you. It’ll also tell you how to test the sensor and the fan, so you don’t waste money changing the wrong part. And it’ll tell you which is the AC-operated fan and which is the fan operated by the sensor.

Geez! Your vehicle has three cooling fan relays! Wired in series and parallel circuits. And these are what control the cooling fan speeds. So it could be a problem with any one of these relays.

These relays are located in the underhood fuse block on the right front strut tower. You could try figuring out which relay is causing the problem by testing them. Or you could just plug in three new relays.


Can’t anything just be easy…lol

Thank you

OK, I check the relays and the fuses and the are all good…the two fans I have are not turning on at all…I don’t believe both fans could be bad at the same time, Let me ask you something is the Temperature sensor have a wire that also goes to the starter solenoid.

Thanks Chris

How exactly did you determine that the relays are good?

there is another relay in the fuse box that is exactly the same as the fans (for the ignition) so I took that one out and tried to start it (and it wouldn’t start) so I put in one of the relays that operate the fans and it started…and repeated the process. They both worked. process of elimination.


So if you have eliminated the relays, the next step is to test the fans. Can that be done with a jumper wire? You may have a loose wire lug or a corroded one in the circuit, or do both fans have the same ground wire? It could be a bad ground. A large percentage of auto electrical problems are caused by faulty grounds.

I would also have the temperature sending units checked. Years ago my Saturn developed this problem. When I was stuck in traffic the temp. gauge would go into the red and I would have to turn the a/c on to turn on the radiator fan. It was caused by a temp. sending unit drifting out of range and I finally found the problem when the sending unit drifted so far out that the engine started to run poorly. There was a sending unit for the engine computer, which also triggered the fan, and another sending unit for the temp. gauge.