Hello all, hope you can help with a problem I haven't seen in my searches. Recently I noticed both radiator fans are running on high whenever the engine is running. With key off or in the on position with engine not running the fans don't run, only when engine is running. Does this sound like it could be the relay?

 

Year???? Is the CHECK ENGINE LIGHT ON?????

 

Sorry, I went to edit the post and realized you can't (strange)
It's an '02, no check engine light - temp gauge reads normal.

 

FAN WIRING...

ok.....Since no C/E lamp...we can reasonably rule out ECT (Coolant sensor) as being stuck High....

Now, PCM controls the fan relay...(Which by the way is a solid state control module...and NOT a little Black Cube) during periods of demand...High coolant temp, A/C /Defrost request...etc.

If it only runs with the engine running....we can reasonably rule out stuck relay..because there is No way for a relay to differentiate "Running Power" from "Key turned ON power"

So we move to the other side of the system....Is the defroster on?, is the A/C on?

At this point...we know that PCM is commanding the fans ON....But why???
Either the PCM is defective.....or something is giving false info to PCM , when no Command is actually required.

 

With engine running, it makes no difference whether the ac, heat, defroster is on/off - both fans run on high.

 

Un plug the high pressure switch connector at the A/C line. This will disable the A/C. If the fans now behave normally...you can start looking into the A/C related components as the culprit.