What controls the fan to turn on???

[GRANDFURY]

I know that coolant temp sensor is part of it but is there anything else, like a another senor or something that tells the fan when to turn on? The car is a '89 GP with the 2.8 auto and air. This weekend i'm doing the coolant temp sensor but what else makes the fan go on. My fan wont turn on by it's self so right now I have it hooked up so that when the ingnition is on the fan is on but I dont like it. I'm going to do the thermostat too but is there anything else?

[Guest]

The ECM reads info from the ECT, which at a preset temp, turns on a relay that controls the fan.

[geoffinbc]

On old cars like a Celebrity they had a simple thermoswitch on one of the heads that controls the fan. This is what I am using on my truck...

Buy yes on yours it is the ECM that makes the call. If you have a scanner you will be able to see when the ECM commands the fan "on" or "off"

[Compufreek]

What temp is the 3100 set for generally? It seems to get pretty hot before accually kicking on the fans. Is it the same sensor that reports to the ECM and the temp gauge? When I had an intake leak I swear my fans never seemed to come on as I was over heating but couldn't really tell because I was driving.

[GRANDFURY]

So my ECM might be badd too? I hope not they are expensive around here. Should I use any plumers tape on the coolant temp sensor or just thread it in?

[GRANDFURY]

Is the ECM that is what controls the spark and is ounder the coil paks right? Or is it the computer?

[Compufreek]

I have a 95 GP and the ECM is in the engine compartment on the passenger side Front just behind the light. Don't know if yours is in the same place but at least its a start.

[GRANDFURY]

Yeah, it is the computer I just remembered that the other is the ICM. What is the coolant temp switch ? Is it the same as the coolan temp sensor or is it something different? Car is 89' GP LE.

[Compufreek]

That is what I was wondering. I didn't mean to hi jack but figured it was the right place to ask my question to. My temp gauge can show me overheating but I am almost certain that my fans didn't kick on.

[GRANDFURY]

I have a cheap little multi-meter is there any way to teast the ECM?

[Manitcor]

my ECU wont turn on my fans properly either, apperently its a common problem. I hooked the fans up to potentiometers with temp sensors and mounted the sensors to the radiator housing. I can adjust when they come on from under the hood. Great for when seasons change and I dont need the extra switches in the cabin.

[Anonymous]

The ECM looks pretty complicated to me.. i dunno if you can really test it, especially with a cheap multimeter.

The fans do kick in at a higher temp on our engines (I thought something was bad on mine, but it was just running bad cause needed a tuneup).
If you want, you can test out the fan motor. Just connect the battery directly to it, and be careful you don't hurt yourself! :P

[Compufreek]

Yeah tested my fan and he's right they are quick and the power likes to arc to them, LOL. Mantincor do you have pics of your setup or maybe more detailed instructions. I was gonna set my second fan on a switch in the cabin but if there is a way to do it under the hood then I would rather do that. I have also been thinking about getting the fastchip reprogram, he says he lowers the fan on temp on top of getting better performance.

[Manitcor]

no I dont have any pics, but Ill try to snag some tonight on the digi and get them up by tommorw, its a pretty simple setup just splicing into the fans ground and giving it power from thorugh the module as opposed to the ecm which does not work properly on my car anyway.

I may need a new ecm soon actually, I noticed lastnight that my revlimiter does not seem to work anylonger, while cool it worries me that I did not set the computer up to do this.

Anyone got any ideas about hooking up an older odb1 computer to replace my odb1.5 POS

I have no maf and am running a 3400 with a 4t60-e on the stock harness.

[GRANDFURY]

I know that the fans turn on at a higher temp then other cars but mine kept getting worse and worse till it wouldn't turn on at all and I have too crank the heat on or shut the car down but if I shut it off it might pull it's little stalling game it likes to do. It only has ever overheated at idle as when it stalls. So this weekend i'm going to put in a new temp senor and try the ECM from the junkers new thermostat and flush the rad again, then do an idle relearn and HOPEFULLY THIS WORKS. alt. next week too I hope.