I have a 92 Trans Am and my fan turns on when I turn the key without starting it.

I never thought much of it until I read on another forum that its actually an issue and could be related to shocking the ecm or the chip prom not being recognized? I've had the car for about 10 years now and for as long as I can remember the fan runs all the time. But around the time I got it, back when I was in high school I had a jumper cable accident. My friend and I was jumping it off and I was in the car, my friend let the hood drop on the jumper cables while hooked to the battery. There was a loud pop and flash and then after that the car ran bad and the lights flashed. I had burned the ground that's attached to the body. I replaced the cable with a doubled up amp wire. But one of the problems that would happen a lot while the ground was damaged was not idle on its own, it would run but I needed to keep my foot on the pedal. After fixing the ground this issue would happen sometimes. Could some of the issues be from shocking the ECM or not properly grounding to the body? Any help would be appreciated.

 

is ur ac on? that will turn the fans on and keep them on with the turn of the key

 

AC is off and the fan still runs

 

Same thing here, I assumed fans always came on before engine...

 

for a single fan tbi car, the fan switch on the passanger side head going out , or the wire that goes to it grounding out will cause the fan to run anytime the key is on. since your car is TPI, the fan is controlled by the ECM. which the fan constantly running is an indicator the ecm is in limp home mode. possibly from the battery incident. is it throwing any codes?


on a side note "doubled up amp wire" is not a suitable battery ground. go to the auto parts store and get a new ground cable.

 

Fan run is typical of ECM/memcal problem but several things to check 1st
Has PO wired the fans to run ; key on?
Many uninformed guys think this is the cure all for temp problems
Is A/c switch functional?
If it is faulty then as noted above can cause fans to run

Any codes showing?

 

I've got an 89 GTA and mine does this as well. The fan comes on as soon as the key is in the on position. Never thought much of it either. My AC is turned off as well. Weird things...

 

There's no codes on, not sure if the AC switch works or not I don't ever use it, I just use the trusty 260 AC. Do you mean the switch by the cd player or a different switch? I'll need to check the fan wires when I get a chance. Thanks everyone so far for the help with troubleshooting this. Probably my first thing to try is replace the body ground with a new one.

 

Not a expert on your particular car but usually there is a pressure switch on a A/c line ( under hood ) that tells the ECM that the A/c is working so ECM turns the fan on.

If that switch is faulty then it may be indicating to the ECM A/c is on when it is not

 

theres a pressure switch on the ac lines by the dyer. on cars that have the fan controlled by the ecm it sees this switch activate and turns on the fan. on single fan tbi cars where the fan is controlled by the fan switch, this ac pressure switch is wired into the fan relay to turn the fan on when the ac is going.