1986 Corvette

Hey dad angel, im still processing this but if the fan is coming right on, lets try and pull the coolant temp sensor connector off, its located on the side of the left cylinder head, lmk what happens

jim

Ok well back to basics, check for fuel pressure, fire on all cylinders, also check the alternator output and battery voltage, basics are the best place to start with a weird problem like this, I wish I was standing right there so I could see whats going o, yeah check the basics first and let me know what you find if anything and you can ground out a and b terminals on the dlc connector and check for codes use a bent paper clip and count the flashes, they will be two digit it will flash 12 in the beginning and the end of the sequence

thanks
jim

Did you ground the two terminals together? If so the check eng light did not flash? I just want to make sure you are grounding properly before we move ahead

jim

There is also a cooling fan temp switch on the right rear of the engine and a cooling fan relay on the left side of the firewall under the master cylinder, i can check wire color if you need it, i would like to figure out this fan deal before anything, ac and defrost is in off position??? i think were in the right direction , the ecm seems fine, pull connector for temp switch , then check the relay to see if it is working or it is stuck on.there is an a/c pressure switch on the rear of the right fender, wires are black on one side and dark green on the other , the green side feeds signal straight to the ecm and in the ecm there is a relay it goes through and then out to the relay and it splits to a red wire fuseable link on one side and fan mototr on the other

without being there its tough, i really think there is something in this circuit causing your problem, if the ecm somehow thinks the engine is at operating temp it will turn the fan on , this would cause the engine to run rough, but there still may be another problem thats why i would focus on the fan issue first ,
sorry for the long post but this one deserves it

jim

Thanks,
so you pulled the connector from all of the components I have listed above even the ac switch one at a time and replugged them before moving to the next, something is giving that fan power when it shouldn't have it and I have listed everything in that circuit hmm, its one of those components or a short to ground between them and as far as being female, your a person you can do this, btw you can save that pic of the diagram and blow it up some on your computer, I thought it may help you

the other way to check if you have a test light or dvom is to pull the connector off og the fan which obviously has power and run a backwards check with the test light and move from component to component checking power and ground from each, what I mean is if you turn the key on and pull the connector for the ac fan switch and the fan goes off wahlah if not plug it back in and move to the next component in line, the ac switch is before the ecm and sends a signal into it and goes to an internal relay and then out the the other components

i also found there is a blue wire from the fan fuse that runs down to the generator and back up through the charging system, is it putting out 13+ volts?

I may be repeating myself but I wanted to make sure the charging system is putting out more than 12 volts and the battery is good because if you replaced the ecm and checked the other components as I stated and the fan did not go off, the only other item was the generator, I also wanted to make sure this was all done with the key in the on position where the fan was running,

thanks
jim

I Believe the most common cause of this condition is a failed relay, Namely, one containing a contact set that's welded together.

Good luck.