My battery light turn on and my power steering stop working on my 325 ci bmw 2001

SOURCE: Replace battery in key

If you have the diamond shape key, the battery is not replacable. If you have the square shaped key, the battery is replacable, but that is obvious because of the screws on the back of the remote.if you have the diamond shape key, it is recharged when its inserted into the ignition. If the key hasn't failed, taking a long trip 60 min. or longer should recharge the battery. If there is no change in the operation of the key after your long trip, most likely the key has failed and needs replacement.

SOURCE: How do I disconnect/remove the wiring of the passanger side mirror on my 2002 BMW 325 CI?

the mirror is easy, theres a trim panle on the inside of your car exact oposite the mirror (it's the mirror of were the mirror should be)
remove that and there you go.

To get to the Wireing you need to remove the door trim panle. do you know how to do that ? and do you have auto windows ?

SOURCE: fan stay on after car is turned off, runs down

fan module is bad

SOURCE: 325 ci bmw belt diagram

The belt diagrams are usually on the underside of the hood or on the crossmember at the front of the engine bay.

Regards,
matt

SOURCE: what kind of power steering fluid should I use for

I know E46's use ATF (Automatic Transmission Fluids) for their power-steering systems. BMW Reccomends to use a common Dextron III / Mercon Automatic Transmission Fluid.