Ok, so there is no air coming from the vents if i understand this correctly.
Well this happened to me a few months ago and after phoning BMW i noticed that i would rather diy the problem then give them a kidney for the fan.
This is what i did and do suggest do this first before doing anything else.
Required: Q20 and a straw
Method: Open the bonnet and remove the (think) 8 screws that holds the pollen filter in place, the thing that is in the middle of the car just below the windscreen under the bonnet. Remove it and then look in the passenger side. You will notice a hole with fins if they are open, if not then just set them up in the car, start the car, switch the fan from auto to the centre fan and top fan, switch the car off and notice the blades at the hole has opened and you can see the fan now. With a long screw driver (please work careful here not to damage anything) now try and move the fan in a anti clockwise direction. It should be stuck and hard to move, this is normal as the middle rod rust over time and the fan stops. So with the straw and Q20, spray Q20 into the straw and hold the one side close, with the other side put it onto or as close as possible to the centre of the fan and let it drip on it. With the screw driver try again to move the fan anti-clockwise and if it let go. Stop with the Q20. Now go back into the car and start the car up. You should have a fan now.
Keep us updated and this worked for me.
