2009 A4:

For several months my car has had a musty smell that immediately comes out of the vents when the AC turns on. It goes away pretty quick but it is pretty potent. I took it in to an independent place I use for the 65k service and brought it up to them thinking I needed a new filter or something. He called me and said Audi has an information ticket or whatever regarding the issue. I paid $120 for them to spray something in the system to "kill off" the mildew that was supposedly causing the issue. Well, that worked for about 2 days. For those 2 days I smelled a "Febreeze" type smell out of the vent, but now I get blasted with the mildew for a few seconds and it goes away. Any advice on how I should handle this? I called my guy and he said "they could try replacing the filters", but I'm opposed to "trying" more things after already dropping $120 on something that didn't work.

Thanks