Alright so first off i couldnt find anything on here stating what cars had a single electric fan, mine had the bearings go bad but after checking 4 3rd gens i finally found a 88 v6 bird that fit exactly. Anyways it did this before i replaced the fan, a few times the fan cut on with the key in the on position, today i noticed the fan cut on around 120*, now i noticed the temp sensor on the driver side head had a little bit of corrosion on it, could that be causing it? Im gonna clean if off tomorrow but just curious if extra resistance would change the signal tricking the ecm into cutting the fan on.

 

Early tpi (85-6), lg4 (86-7), Tbi and v6 got single fans (iirc).

The coolant sensor for the ecm is on or near the thermostat housing.

The coolant fan switch is what you found. It normally closes to ground (the head) at 238°F. The ecm has no control of the fan for tbi cars. The hvac controls set to any a/c position will cause the fan to run as well.

The switch can go bad and stick closed or cause early fan operation. Its n
more normal they go bad and stop working.

 

Well i didnt get around to messin with it today but every time i started my car today the fan came on instantly, if all the switch does is close the ground at a certain temp there probably aint a way to check it with a multimeter is there?

 

If you disconnect the connector to the coolant switch, you can check if it's closed by checking the resistance between the contact in the middle of the switch, and the head itself. If you have 0 ohms, you know the switch is closed which makes your fans come on.

Probably the easier thing to do is to disconnect the connector at the coolant switch and see if the fans come on. If they don't come on at any temperature with the connector disconnected, you're switch is bad. Otherwise if the fans come on with the connector disconnected, something else is making your fans come on.