nhdoc: Even MB dealers are not exempt of making erroneous diagnostic, mistakes and unnecessary repairs.
Last fall, my heater blower motor just quit working when I was 400mi. from home. I stopped at a Benz dealer for help (outside temp. was near 0deg.C) After checking, analyzing the problem , plugging-in various testers, they finally came with a diagnostic....fried blower motor and possibly a fried blower controller.
Thankfully they did not have the necessary replacement parts in stock and I left the place.
When I got back home, I stopped at my independent shop without having an appointment. He just made a quick check in the yard and found within about 30 seconds that the problem was caused by a burned fuse (the flat fuse on the left fender.)
3 minutes and $1.50 later, the blower had magically resuscitated.
Diagnostic at MB dealer : 1.2 hours at $85.00/hour, + shop supply (?)$10.20 + taxes: Total:$120.05