Auxiliary Fan write up

[Schickeneder]

In case anyone is planning on doing an aux fan replacement, avoid the cheap auxiliary fans. Here's why:

After the blades shattered on my oem fan I bought a cheapo off ebay (~$160.00) and it lasted a little over a year. One day after getting back from a business trip I noticed my battery was completely dead (no dome lights, nothing). After I jumped the car I heard the auxiliary fan turn on full speed--temperature was fine at this point, as I had just started the car. The fan was stuck always-on, even when the ignition was off, I guess it always has a hot +12vdc.

So it seems the PWM/controller died. I noticed on the cheap fan that the control module was attached to the fan frame, whereas the oem fan has it integrated into the motor assembly.

Now, with that in mind, you may just want to gamble since the OEM fan costs about twice what I paid for the cheap one, you can still afford to replace it twice (of course the labor isn't very fun) before losing money.

Note: This was on a 2000 528i with the PWM contolled fan, not the resistors.

[JaimeZX]

Just did mine yesterday. Ordered the OEM/Behr fan and resistors from Autohausaz.com. ($178.12)

Couldn't for the LIFE of me figure out where the resistors ($70.34) go.

Finally I saw that the original fan had the resistors mounted on the back of the frame... and sure enough when I looked at the NEW frame... there were resistors already there!
So those of you planning to do this - if you determine your fan is dead and not just the resistors, you only need to order the fan!

So I have $70 resistors to return.

The whole job took me about two hours, but I was working alone and cleaning as I went. I could do it again much faster.

[steveng1993]

Thanks for the DIY write up.
I just did mine. It was not difficult at all.
My condenser was filthy and full of debris.
Even with the cleaning it only took me an hour and a half. I think tomorrow I am going to tackle the vanos seal.

[mattmichielsen]

Thank you so much for the detailed write-up. It only took me about a half hour to get everything apart. The 2000 528iT I bought two days ago got pretty hot today. Fan was fried, blowing fuses. Tons of crap behind fan and all over condenser. Anyway, thanks again. Now I just need to find a new fan....

[aamer415]

Great write up and I have a 99' 540i and it still was easy!! took me 2 hrs... everything finally works like it should!!!

[wheelgarage]

Just replaced the fan last night. This post is one of the reasons why this forum is invaluable.

[OnTheFence]

How can you tell what type of fan you have? PWM or resistor?
Also, do most people replace the entire fan assembly, or just the electrical resistor part that fails?

[Lewisjrfamily]

If you need to quickly test your Auxiliary fan, I have just found a really easy trick.
Assuming you have the radiator mounted temperature switch with 3 pins.
(link to image courtesy of Activant)
http://c2c.activant.com/ctoc/index.j...cKFxAxNFV1BhgA

The switch is essentially two switches end and centre connected in series...
.
Something like: . _ \_|_ \_.
(contact - switch - centre contact - switch - contact)

So unplug the connector on your radiator, take 3 pins, insert 1 in each of the contact holes (they fit snugly).
Make sure the pins do not touch any part of the car.
Switch on the ignition, but don't start up the engine.
Keeping hands clear of the auxiliary fan, pinch all three pins together to connect them.
The fan will spring in to life if it is working!

This worked like a champ...the fan came to life, but the AC still blows hot air. Does my temp sensor need to be replaced?

[martz87]

If you need to quickly test your Auxiliary fan, I have just found a really easy trick.
Assuming you have the radiator mounted temperature switch with 3 pins.
(link to image courtesy of Activant)
http://c2c.activant.com/ctoc/index.j...cKFxAxNFV1BhgA

The switch is essentially two switches end and centre connected in series...
.
Something like: . _ \_|_ \_.
(contact - switch - centre contact - switch - contact)

So unplug the connector on your radiator, take 3 pins, insert 1 in each of the contact holes (they fit snugly).
Make sure the pins do not touch any part of the car.
Switch on the ignition, but don't start up the engine.
Keeping hands clear of the auxiliary fan, pinch all three pins together to connect them.
The fan will spring in to life if it is working!

Where in the heck is the radiator mounted temp switch. They sell one for my 01' 525 but I cannot locate the bugger to try this trick. Also trying to locate the fan plug so i don't have to remove the bumper to test power there also. Any suggestion is appreciated. I cannot find it on realoem. My fuses are fine and I'm hoping it's just a sensor or switch at this point.

[bluestu]

I replaced the FSU and still no fan

I've found the fuses 75/76 but how to access them ??

do they drop down or do I take the glove box side connectors off to get back there and if so - how??

thanks and my apologies if this has been covered.....

[JaimeZX]

They don't drop down, you have to reach up behind the other fuses. Kind of a PITA.

[540iEP]

Great guide. Helped me replace my aux fan this weekend. Thanks!

[Yonkers320is]

what if instead of removing the fuses I just disconnect the battery? or is the fuse removal necessary?

great write up, mine is shot, and will probably change it in the fall. The A/C works fine unless I am stuck in traffic when the pressure shoots up due to no working auxiliary fan

[BobPhx]

Great write up! M5 was slightly different but no big deal, still finished in record time thanks to the pics and details. Thanks!