CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Electric fans do not run

My 2003 impala fans do not run without a/c. I have replaced the fans b/c one motor had failed. I have also replaced the coolant temp sensor, all 3 relays, checked for leaks. Unplug the sensor and the fans run on high. Otherwise, they run on medium with a/c on or not at all if a/c is off. PCM?

I’m assuming that when you unplug the sensor that you are talking about ect sensor?If you unplug ect and fans fun, I would not condemn pcm because its telling fans to run with ect unhooked. When you disconnect ect you are basically telling pcm the engine is hot. The higher the temp the higher the resistance. Replace sensor and see if that fixes your fans.

I don’t think the PCM will turn on the fan unless the coolant temp exceeds a certain limit. Are you sure the temp limit is being exceeded?

ECT? I’m assuming that’s the coolant temp sensor on the front of the block. I bought a new GM sensor and swapped it before this post. No change. What’s the chance that the new sensor is bad too?