You are low on freon, the question is why, only two reasons to be low, a leak or someone let out some freon. I bet you have a leak. I had the same problem. I recharged it a few times but the problem returned. I finally replaced the evaporator and no mare leaks. Did it myself, it not easy, the dash has to be removed. $2100 sounds about right for someone to do it. Here is a link to my DIY http://www.xoutpost.com/bmw-sav-foru...ement-diy.html