I have a 2006 E350 that has developed a noticeable musty/mold smell emitting from the a/c system. Car is under warranty, dealership is just changing parts in hopes of stumbling across the problem. To date they have changed the cabin air filter and done the service bulletin on system clean-out, replaced the condenser (left out some MAJOR, blue, 12 point bolts found under the mat). All seat bolts are installed and are black in color.

Anyway, now I notice a distinct mold smell coming from the front, outside area of the car when it's parked in the garage. I have been on my knees crawling all around the car and cannot nail the source. The dealership service writer is useless as I probably could leave a voicemail for the mechanic and probably do better.

Car always garaged in Palm Beach area.

Any clues?

Thanks.