High speed fan not coming on at commanded temo

davec73

SCCoA Member
Hey guys I have had the same problem with my high speed fan not coming on since I put the engine in the car which really holds me back from driving it.
Here is what I have done to diagnose it:
1. tested the fan to ensure it works at the connector
2. Jumped the wire at the IRCM to ensure the wiring is good
3. Replaced the IRCM
4. Replaced ECT sensor
I do not have an IRCM tester so I don't know if the one I replaced the original with is any good but the low speed fan comes on as it should. When I get the car out on the highway when it is hot out and beat on it to were it goes above the heat range of the low speed fan settings the car starts to heat up and the high speed fan will not come on. The settings in be are on at 198 off at 190 and I moved the high speed settings to 254 to make the low speed stay on at all times. All I can think of is that I may have an issue with the EEC not commanding the fan to come on because it is bad. If anyone has an IRCM tester that I could borrow or buy please let me know as it would allow me to eliminate that and narrow it down to the EEC as the definite cause.
 
I don't know 100% for sure but the low speed is the only speed that comes on when you hit 198 degree's,the high speed should only come on when you run the a/c. If the fan is coming on at 198 and shutting off at about 190 that is exactly how they run from the factory,if you want to see it run cooler I would get a 180 degree tstat and the tune for it from dave dalke.
 
I don't know 100% for sure but the low speed is the only speed that comes on when you hit 198 degree's,the high speed should only come on when you run the a/c. If the fan is coming on at 198 and shutting off at about 190 that is exactly how they run from the factory,if you want to see it run cooler I would get a 180 degree tstat and the tune for it from dave dalke.
No the high speed fan is set to come on at 228 from the factory and shut off around 218 I think my car has qtr horse and that is what the high speed fan settings are set at. the low speed fan is what comes on with the ac not the high speed.
 
All you need is an Ohm meter and you can test your fan motor.

Turn off the car and carefully disconnect the fan motor pigtail. Check the resistance between the fan motor connections. Resistance should peg the scale between two the ends and the center wires. One end is for high speed while the other is for low speed.
 
All you need is an Ohm meter and you can test your fan motor.

Turn off the car and carefully disconnect the fan motor pigtail. Check the resistance between the fan motor connections. Resistance should peg the scale between two the ends and the center wires. One end is for high speed while the other is for low speed.

It says in my first post that I have already completely tested the fan and it works replaced ircm an ect sensor. Also tested the wiring and fan function per the ford evtm. Hwystar sent me his ircm tester and I have another eec for it so we will see.
 
I know you said you put in a new ECT. But wouldn't it be possible that it is out of limits enough for it to barley kick the low speed fan on, and it never get high enough to kick the high speed fan on? I've gotten bad ones brand new before, it's just a thought I had.

Also, I hate to ask the obvious, but you did replace the ECT for the fan and not the gauge correct?
 
I know you said you put in a new ECT. But wouldn't it be possible that it is out of limits enough for it to barley kick the low speed fan on, and it never get high enough to kick the high speed fan on? I've gotten bad ones brand new before, it's just a thought I had.

Also, I hate to ask the obvious, but you did replace the ECT for the fan and not the gauge correct?

The low speed fan works perfect guys. The problem occurs when I get on the car and drive it hard. If the car gets above the temp where the low speed fans cant kick on anymore the high speed will not come on. However I have verified through the ircm wiring by jumping the relay bk/o to br/o that the high speed fan works and the wiring is good. I have also replaced the ect sensor. SOOOOOOOO if the ircms check out to be good the only other culprit that could cause this is the EEC correct?
 
I understand that your fan works perfect, but I still think you could have a slightly out of range ECT and not being able to kick the high speed on.
But yes, if all wiring is good and the high speed does work and the IRCM test good, that yes, the only thing that controls that would be ECM.
 
Last edited:
I understand that your fan works perfect, but I still think you could have a slightly out of range ECT and not being able to kick the high speed on.
But yes, if all wiring is good and the high speed does work and the IRCM test good, that yes, the only thing that controls that would be ECM.

Well ive put an aftermarket ect sensor in it when I rebuilt the motor but I just replaced it with a motorcraft. I have another EEC to put in it as well so hopefully fingers crossed one of the two fixes it.
 
Well ive put an aftermarket ect sensor in it when I rebuilt the motor but I just replaced it with a motorcraft. I have another EEC to put in it as well so hopefully fingers crossed one of the two fixes it.



Hopefully that fixes it. I really can't think of anything else it could be.
 
First off, the fans should not operate while the car is at highway speeds. Secondly, you said in the first post that you've moved the high speed fan settings up to 254*. You'll need to lower them to the desired on/off temps.
 
First off, the fans should not operate while the car is at highway speeds. Secondly, you said in the first post that you've moved the high speed fan settings up to 254*. You'll need to lower them to the desired on/off temps.

Yeah I know they wont work at highway speeds unless the ac is on, the low speed fan kicks on. It tends to overheat after ive been on it and slow down below 43 when the high speed fan should kick on Rod. I have the temp settings back to 198 on 190 0ff and 188 on 178 off right now and I am probably going to lower them even lower so I can see the high speed fan cycles.
 
Did you make other EEC program changes before the overheating issue? If so, what else did you do?
No the fan settings are the only thing that were changed. It has done this evrry since the new motor has been in if not before that. The eec is suspect to me because its a remanufactured unit. I have changed the ircm but don't know if either are good however the ircm tester should eliminate the ircm. If its bad I will probably take it to my local electronics shop and have the relay replaced.
 
Sorry if I missed it - what year SC?

Did the new engine include any painted/pdr-coating accessory brackets?
 
Did the new engine include any painted/pdr-coating accessory brackets?



Not to sound rude, but what would that matter. I know the DIS module has to make contact and you have to use heat sync and make sure it's grounded good, but isn't that just sending signals from the EEC for spark and timing? I could possibly see heat input, but that's thru the IRCM to the EEC correct?
 
Yes everything has been painted and powdercoated and all places where any grounds should be have been ground down to supply sufficient ground. The car is a 92
 
Not to sound rude, but what would that matter.

Grounds matter - a lot w/these cars…they can be pretty picky:) I doubt the ECT sensor on it's own would care. I let a new one fool me for months last year.

It sounds like the OP took pains to at least be aware of the need, tho. Might be the EEC in this case, perhaps. Even it has it's share of grounds it relies on :)
 
Last edited:
No the fan settings are the only thing that were changed. It has done this evrry since the new motor has been in if not before that...

The reason I asked this question is to see if something changed. Changing your EEC fan settings seems to be an BAND-AID® to me... It could be that your cooling system just may need an upgrade to match the new motor. Maybe the radiator is a tad old. SC radiators are small and do tend to gum up over time. :confused:

I would check my coolant temperature resistance just to be sure. Yea, I know you have a new one. But I never trust anything that was not tested. If the ICRM is good, the ECT resistance is correct and your high speed fan goes on and temperatures rise I would suspect my radiator, water pump and or thermostat as being weak.
:eek:
 
Back
Top