Hello. I know this is an old thread, but it seems to apply to the issue I am having.
I have a 2000 328i. The heat on it does not work. Or, does not work most of the time i should say. I can turn it on and the blower works, but no heat. However, on two occasions, it did work. And sometimes, when the heat is not working, I can turn of the windshield defrost, and hot air will come out.
I see where smolck suggested vacuuming out the vent by the climate control panel. I thought I would try this, but I am not sure where this is located. Can someone give me some details?