I have a 99 grand prix that has 106,000 miles on it. My car overheats at idle because the cooling fans don't turn on. One however does come on whaen the a/c is turned on. Also when I unplug the plug from the sensor both fans come on but the temp guage goes out. When i plug the sensor back in the temp guage starts to work and both fans stay on until I turn the car off and restart it. The fans do not turn back on. I have replaced the sensor and have checked both relays and they are fine. The man at autozone told me that there was another sensor to control the fans but i can't find it and my haynes manual doesn't show it. thank you very much i would appreciate the help