Possible Aux Fan Switch Failure?
 

Hey there everyone! Got a quick question..I have an 03 X5 and for the past week, when I start the car, the aux fan runs at full throttle for about 30 seconds, then it just winds back down to normal speed. It only does this when the engine is cold. I make sure I don't crank it with the A/C on, but when I do turn it on, it works fine. Any tips? I was thinking it could be the auxiliary fan switch, since the fan itself seems to be spinning properly.

Whatcha think!? :dunno:

Normal. That is a self check by the car that the fan is working.

Really?? It just started doing it and I've had the car a good while. It definitely doesn't seem normal. People probably think my car is about to explode!

Yes it's normal. It is a self check done only on cold starts. I never noticed it too till my fan died and I started research on diagnosing the system lol!

Upon research, some ways to check fan function is that the fan should go high speed when MAX AC is engaged, and go high speed for a few seconds on cold start up.

There are no switches in the system, the fan is controlled directly by the DME via a signal wire.

I guess I don't understand why it just started out of the blue.

Maybe you just didnt notice it before? I never noticed it did that with all the noise the car makes on start up like the air pump and fan clutch.

I need to get a video...I think this is louder and different than you think. This is incredibly loud. Not like it just getting "warmed up" or anything. I will try to get a video tomorrow morning.

Yes a video would probably show if anything is amiss.

Try to compare fan speed at cold start and fan speed when you turn on MAX AC. They should be the same. At both instances fan is at maximum speed.

If you have a fan switch failure be prepared to shell out some BIG BUCKS. The fan is controlled by the DME.

Grabbed a video this morning so y'all could hear it. https://youtu.be/u10F4lYYRSA