Thanks for the feedback. Do you know if that is what is used to switch between the hot and cold air functions? I'm guessing that the passenger side control also controls the rear seat vents so that would make sense.

I had read this thread where a poster said his problem was the "water valve" but I'm not sure if this is the same thing we're talking about on the left strut tower.

http://www.xoutpost.com/bmw-sav-foru...ditioning.html