I had a problem like this, but it would only happen sometimes or the a/c wouldnt turn on at all. I think the next service they replaced an air filter, or some type of filter not sure what it was. It's fine now. But don't take my word for it, I'm sure someone will reply soon.

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2001 X5 4.4i Sport (Moms)
2003 Acura RSX (Sisters)
2003 M3 (Mine)
2008 M3 (Coming Soon)