I have replaced all coolant relays and components and my cooling fan will not work unless my ac is on.Any suggestions on how to fix or what the problem could be?


Asked by Aug 21, 2015 at 09:25 PM about the 2002 Pontiac Grand Prix GTP

Question type: General

Its also supercharged

13 Answers


Is the engine overheating? The fans will come on at low speed when the coolant temp reaches approximately 220°F. As the temp continues to climb the fans switch to high speed at about 240°F. If the fans won't come on at all have you replaced the coolant temp sensor? If so, it could very well be a faulty PCM. HTH. -Jim

Best Answer Mark helpful

Yes I replaced the temp sensor also and fans still aren't coming on

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There are 2 temp sending units, one for the gauge etc., and another for the cooling fan control


I changed the one on the block where would the other one be


Probably near the thermostat, that's where it is on my 2000 GTP.


That's the one I changed it goes into the block by the thermostat


Not on this vehicle. One sensor for both the PCM and the dash gauge. HTH. -Jim


Thank you Jim

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You're welcome. Glad to help. -Jim


If you have replaced the sensor, all the relays and "components", sounds like your going to have to trace the wiring. GOOD LUCK!!!


Since the fans will come on when the air- conditioning is on we know they can work. Without the air-conditioning on the PCM is supposed to complete the circuit to ground and start the fans. The PCM determines when to do this based on information it receives from the coolant temperature sensor. If anything it could be the wiring going to the PCM from the coolant temperature sensor. Otherwise it's most likely going to be a PCM problem. Ideally someone needs to plug into it with a scan tool and command the cooling fans on. HTH. -Jim


This is true, but if it were mine I'd check the wiring from the sensor to the PCM, heat and engine vibrations can cause a multitude of problems with small wires in tight places. Enjoy!!

1 people found this helpful.

You haven't mentioned whether the car actually overheats. The fans rarely come on on my '03. Maybe its just not getting hot enough to need them. Maybe you're trying to fix something that's not broken.

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