The electric fan on my car always used to kick on at about 220*, and stay on until it had cooled the engine down closer to 180* (or so). Now it won't come on at all, even though the temps are rising above 220* during prolonged idleing.

With engine off I grounded A and B terminals on the ALDL, which causes the fan to kick on automatically. This tells me the fan and relay are okay, but it doesn't fix my problem. All I can figure is that a sensor is bad or the ECM. I have 3 sensors that plug into my coolant ports on the head. I have identified 2 of them as the ECM coolant sensor and the temp guage sensor, but what the heck is this 3rd one for? The fan maybe? My Haynes manual doesn't show it anywhere (ha! Imagine that!). It is located at the rear of the head on the passenger side and has a 1 wire connector going to it.

 

That's the one that you need to replace. That's the Fan Switch.

The 2 located next to the thermostat are for the ECM(2 wire sensor w/yel and blk wires) and the other is for the guage/idiot light.

 

What is the one that is located at the rear of the passenger side head for?

 

the fan on all but the 85 model year. 85's dont have a fan switch from the factory. they added it on later years cause the fans sometimes will not turn on as they should by the ECU alone(i should know, my ECU wont activate the fans)

 

Got a new one and put it in today. Fan is working properly again.
Thanks for the help, guys!

The first time I went in and told them what I needed the genius behind the counter couldn't find it. He then wanted to sell me an aftermarket fan control switch and relay to wire in instead. I told him "why create more wires and parts under my hood when I have a perfectly good, tidy wiring harness that works fine? I know the part I need exists, it's just a matter of finding it."
Honestly, I don't understand people like that anymore.

 

Luckily my local parts guy is a regular on these boards (Iansane) and he knows thirdgens!

 

"""getting beat by truck's""""

Is that a joke dude? i know my 3.1 aint realy Fast" but damn sounds like somthing wrong with yours.......

 

Kansas has no Emissions so its kinda hard to find stock trucks around here, and ya i have a vac leak or something. I also think that i have a bad injector that is causing the car to run WAY rich.