Intermittent cooling fan not working

CHICAGOBOB

MEMBER
2006 LINCOLN LS
3.9L
V8
160,000 MILES

Cooling fan rarely coming on causing overheating within 15 miles of driving. Also doesn't come on when A/C is turned on. With 90° heat selected on climate control "auto" setting the A/C light is lit. Manually set to 90 and A/C light goes out but system blows not nearly as hot as it should. Drive for 15 minutes and car will want to overheat if the fan does by chance come on it will lower the temperature and at least let you get home. All this is done on an 85 degree day.
Thank you!

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

If the fan is working sometimes then we can assume (for now) it is not the fan itself. However, we need to check the voltage at the fan on the white/black wire from the PCM, because you have a micro processor as part of the motor.

https://www.2carpros.com/articles/how-to-check-wiring

Also, I just want to confirm you have the single fan set up and not dual fans?

If you have dual fans then this is a different issue. However, I suspect you have a single fan, so if you do not have voltage at the motor when the fan should be on, then we need to make sure the cylinder head temp sensor is working. If the engine is actually overheating or the gauge is showing that it is overheating then the fan should be coming on.

At that point, the PCM is the likely issue as it should be commanding it on and it is not.

Below is the wiring diagram that will show where we need to test this voltage.

Please run through this and let me know what questions you have.

Thanks

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