Electrical Cooling Fan Issues - Intermittent Check Engine Light

[SunrayG19]

I am new to this forum. I have a 94 Mustang GT, 5.0L with some cooling fan issues.

Initial Problems: The Cooling Fan was failing to turn on when the engine was hot causing an overheat condition. This was an intermittent problem. I discovered the cooling fan pigtail ground was melted. Replace the pig tail, problem solved temporarily. Car is overheating again because the fan doesn't turn on when the engine is hot, but pigtail looks new still.

I have replaced the Coolant Temperature Sensor (is there a requirement to purge the air out of that fitting when changing the sensor)? I have now have a check engine light that turns on solid with the fan, and turns off when the fan stops. The car was running an aftermarket temperature guage. I have attempted to replace the factory temperature sensor that feeds the guage based on the advice of a Ford Mechanic. The factory gauge is not serviceable, likley why the car was running an aftermarket gauge.

The Cooling Fan now turns on a few seconds after I start the car and runs when the car is cold. It does cycle off eventually, and I still have this check engine light turning on and off with the fan (solid light, no flashing).

A KOEO test functions that fan properly. There is a code 118 - Engine Coolant Temp Sensor over max voltage, which appears to be connected to my overheating issues. I also have a 212 Sprout circuit ground, which I believe was connected to a TFI problem - no spark. I replaced the TFI module, that problem is fixed.

Any idea why my fan seems to run when the engine is cold and is throwing a check engine light?

The Car runs a little rich at idle, but otherwise starts and drives fine.

 

[General karthief]

Does your ac work and if so does the fan start up when ac turned on

 

[General karthief]

If you disconnect the ECT electrical connector and start the car, the low speed setting should come on.

If you ground CCRM Pin 17, the fan should come on high.
If you apply fused 12 volts to CCRM Pin 14, low speed should come on.
MAX AC should make high come on.

Checking any or all of that can be telling in narrowing things down.
Copied from a similar post by hissin50

 

[SunrayG19]

The ac doesn't work. There is a leak in the system somewhere, so there is low pressure in the refrigerant. I can't operate the fan that way. I suppose I could trip the low pressure a/c switch?

 

[SunrayG19]

OK. Those tests will confirm serviceability of the CCRM and ECT (which is new).

Any idea why the check engine comes on when the fan is operating?

 

[SunrayG19]

More of this problem. I have a short in one of the wires that connects to the Engine Coolant Temperature Sensor. I will need a new harness. Figuring this out has stopped the fan from turning on when the motor is cold. Still no idea why the check engine light comes on when the fan turns on?

 

[SunrayG19]

Thanks Karthief. Your ECT test diagnosed a short in my wiring harness. Just need to figure out the check engine light.

 

[General karthief]

Thanks Karthief. Your ECT test diagnosed a short in my wiring harness. Just need to figure out the check engine light.

I stole that from hissin50 when I did a google search
Sometimes google make me sound smart
Check for codes for the why check engine light is on, it my coinside with the short you found.

 

[SunrayG19]

Karthief,
I tinkered around the ECT Sensor connection some more and was able to get the check engine light to go out. The fan is cycling on and off the way it is supposed to now. Did a small victory lap around the block!! Thx!

 

[General karthief]

Thats a big thanks to hissin50 and google
Glad to help no matter where I steal the info from.

 

[imp]

Thats a big thanks to hissin50 and google
Glad to help no matter where I steal the info from.

I'm stickin' with my clutch-fan install on my '94, works just fine, no worrisome gauge hippity-hoppin' anymore. Anyway, it made it through summer here with ease, it was in the low 120s many days, gauge never went as high as with the electric fan. Test was to leave it idling with AC blasting away while I ran in to the post office, never a negative peep!
imp

 

[General karthief]

I'm stickin' with my clutch-fan install on my '94, works just fine, no worrisome gauge hippity-hoppin' anymore. Anyway, it made it through summer here with ease, it was in the low 120s many days, gauge never went as high as with the electric fan. Test was to leave it idling with AC blasting away while I ran in to the post office, never a negative peep!
imp

Did you leave a victim, er, passenger in it?
Psa: it is unlawful to leave an unattended vehicle running (ask me how I know this) atleast in FL, oh, and can you guess how many vehicles I've taken where the driver has left it running because 'they where only gone for a second'?
I'm not bashing you for it, just a reminder,
And I'm glad your swap works well, the less electronic gizmos can be ok.

 

[imp]

Did you leave a victim, er, passenger in it?
Psa: it is unlawful to leave an unattended vehicle running (ask me how I know this) atleast in FL, oh, and can you guess how many vehicles I've taken where the driver has left it running because 'they where only gone for a second'?
I'm not bashing you for it, just a reminder,
And I'm glad your swap works well, the less electronic gizmos can be ok.

In the Desert Southwest, a closed up vehicle in 120 degree heat needs about 10 seconds to feel hot as hell inside! Surprised to learn an unattended vehicle running illegal; what if it's locked? Law aimed at attrition due to theft, or safety issue: car goes into gear by itself......imp

 

[General karthief]

Oh yea I agree, I've left my truck running, locked up. Parking brake on.