2000 Saturn Overheating - cooling fan won't run while in idle


I’ve got a 2000 saturn that has been overheating when stopped at a stoplight. First a little background info: I first noticed the problem while in heavy traffic. The temperature would go up and the overheating light would go on. When traffic got going the temp would go down. At some point I noticed the cooling fan wasn’t running. I checked the fuse for the cooling fan and it was blown. I replaced it and it blew again. I then replaced the cooling fan. That solved the fuse problem. Now the fan will run while the air conditioning is on, but the fan won’t turn on when the air conditioning is not on and the car is just idling. The temperature continues to rise until I turn on the air conditioner. The only other thing I can think of would be to replace the little computer that controls the fan in the main fuse bus. Any advice?


I don’t know your car. Most cars have a sensor that measurers the coolant temperature and turns the fan on and off. Some involve a computer and some don’t. I’ll bet that fan is not coming on when you are driving either, but the air blowing in the front of the car will keep it cool enough.

I wonder if an error was made when installing the new fan?

The A/C may turn on the same fan or a second fan. It does not rely on the temperature sensor in the coolant.


Most likely you have a defective coolant temperature sensor. There is a way to test this component if you have the right instruments. Otherwise you can take a gamble and replace it anyway, hoping for the best. It should be easy enough to replace by the owner.


you may have two radiator fan relays, one turns on fan with a/c, and the other on, on engine temp. Possible bad relay.


Thanks for all of the great advice! I’m pretty sure I only have one fan. I have the Haynes manual from other things that I’ve tackled and I’ve been reading about other things online. All of this is leading me to believe it’s the coolant temperature sending unit (coolant temperature sensor). If what I’m reading from elsewhere is correct, they test this kind of stuff for free. I plan on checking on this tomorrow. Thanks again for all of your help!