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2000 Impala

Cooling fan #1 doesn’run. Replaced all three fan relays and cooling temperature sensor which is supposed to turn fan on when coolant temp reaches a certain poin.



Well is the car overheating or what? Some more detail would be useful.

Both fan should run at the same time. The relays switches the fan motors from a series circuit (low speed) to a parallel circuit high speed. If only one fan is running I suspect you have a open series circuit so neither fan is running at low speed, and when it goes to high speed only one fan is running on high. You need to ohm out the motors and circuits to find the open circuit. If you don’t have a clue what I am saying then take it to a shop. You could try swapping motors from side to side, and if the fan motor that doesn’t run moves to the other side then the motor is bad.

The temp gage does not get to the red mark, but the car runs hotter than usual in slow trafic. Failed to mension that I shunted the legs of Relay #1, and both fans run at low speed.

Looking at the wiring diagram. If relay one (Low speed) fails to energize, and relay two, and three energize without relay one being energized then only one fan will run at high speed. This tells me that coolant sensors are ok, and PCM is sensing temperature and trying to do its part. The problem lies on the coil side of the relay, so either the output on the PCM is bad (not good), or the connection between the PCM and relay coil is bad. you already confirmed the relay coil is ok by replacing relay, and fuse good because fans run when relay is jumped out.

Thanks for the help.