I have an 87 IROC, 305TPI/auto. Everytime I turn the key to the on position the fan kicks on. It runs the entire time the key is set to the on position regardless if its running or not. It doesnt matter if the car has sat for 3 days and the motor is cool or not.

I traced the wiring back and did not find any issues with it. The coolant temp sensor appears to be operating correctly.

I checked the engine codes and found nothing at all. Any ideas?

 

Pretty sure its the temp sensor. Did you just get this car and it came with the problem or did it start it recently? If you bought the car and its like that then someone by passed the sensor and wired the fan to your accessory circuit.

 

I was thinking that as well... Would the coolant temp still read correctly if the sensor was bad though? I temp reads perfectly all the time (on the gauge).

Either way they are easy to swap out so I should just change it when I pull the motor.

 

The ECM pays attention to the sending unit at the front of the manifold. It has nothing to do with your temp gauge. If the engine runs good, the temp sensor is probably okay. (but would not hurt to check it)

Could be a bad relay, rewired fan, bad ECM, or any of a number of other things.

Do you have dual fans, or just one?

 

I have dual fans

 

The tab on my coolant temp sensor is broke off so when it falls out, the fan runs all the time.