I have a 91 camaro rs with a 3.1L engine. It has an electric fan and doesn't come on when the temperature exceeds 240 or with the a/c on. I've change both the temp sensor and the relay and neither have worked. I hooked a scanner up to the ecm and it reads the coolant temperature negative, also, when I disconnect the temperature sensor the fan starts up. I was wondering if there is another switch somewhere in the circuit that might have gone bad like a fan switch. If it is, where is it and how can I check it to see if it works. If anyone has any suggestions or ideas, please help.

[This message has been edited by kain274 (edited May 24, 2001).]

[This message has been edited by kain274 (edited May 24, 2001).]

[This message has been edited by kain274 (edited May 24, 2001).]

 

well you know the relay is good with no grounds because the fan kicks in when you disconnect the temp sensor which is the ECM's fail safe mode because it does not know the temp of the motor, so it runs the fan not to over heat. If the scan tool said negative temp with the motor being hot hot then check the ground of the coolent sensor and check the voltage of the yellow wire going into the coolent temp sensor when the car is running. You should also be setting a code 15 (LOW or NO Temp indicated) when you have the coolent sensor disconnect. and if and when you check the yellow wire for voltage with the car running you should get a code 14 (High Temp or Out of Range Temp) because you will be grounding the computer straight through with out the thermistor. If you just probe with a pin on the yellow wire with the sensor hooked up and motor running at 200 degrees F you should be seeing 1.5volts to 2.0 volts in the yellow wire. Either the coolent senosor circuit has a ground in it or the ECM is shot for the coolent sensor circirt or the coolent temp. sensor is not working. The reason I answered your post is I'm trying to low my temp setting on my Camaro, don't for get, the fan will NEVER kick in unless the motor has reached 230 degrees F and/or A/C compressor is on and you are going under 40mph. The only way to change this is fool the computer with a different temp curve sensor or new PROM CHIP. Let me know how you come out.