AUX fan woes
 

Hey guys

I have quick AUX fan question.

So the aux fan in my '06 3.0D is not spinning when the AC is on or when the coolant hits 85c. However I dont think it is the fan itself, as it DOES spin half a turn when the car is started.

So i figured I would call on the vast wealth of knowledge and experience here before wasting hours chasing the issue. given the symptoms, what would be the most common cause of the fan not running when it is supposed to, even though it has power and does spin when the car is started?

Sounds like you need to replace the fan. Here's my DIY guide to get you going:

https://youtu.be/N_K0KPHsteA

Thanks for the link.

I would have thought the fan itself would be ruled out, as it is spinning momentarily on start up as it is supposed to...just not under other conditions?

Foxwell scanner will run the aux fan and I've heard you can force it to spin by unplugging the AC pressure sensor.

It's pwm controlled so you can't run it by applying power.

The part spin at start convinces the computer it's ok even if it's not.

It has to spin more than a half turn in order for it to generate an electrical signal to the DME to know that the fan is spinning. Scan the DME and see if you have a fan fault.

Engine coolant goes near 100 C before it activates the fan. Like suggested test the fan first with diagnostics by activating it via DDE.

I'm not so sure about that. I only thought it turned maybe 1/6 to 1/4 of a turn for its self test I'm going to look a little closer it's hard to do yourself.

NOPE

If you remember your basic electricity, a dc motor free spinning becomes a dc generator. The electrical signal generated by this spinning is sent back to DME. The DME recognize this electrical signal and log the fan as good. If the DME don't see this electrical signal it log a bad fan fault code.

Oh of course I remember motor/generator lessons but ANY motion will create voltage. I was pretty sure I saw only like 1/4 of a turn in the past butt I'm usually not in front of the car to see when the car is started.

A motor has to spin fast enough to create a voltage so the motor must spin for quite some tme and then free spin to create the electrical signal. Spinning only a 1/2 turn will not create an electtrical signal that will be recognize by the DME.

If he could unclip the front grille in front of the fan I would do that and see if the fan spin freely by hand. Could be the fan bearings are shot.