I'm not real familiar with this particular model, but I know that some of the Mercedes radios can be programmed to disable the fader. Mercedes does this particularly for the cabriolet cars that don't have rear speakers. I would talk to a knowledgeable person at a dealer and see what they think. For the radios that are programmable, the Star diagnostic computer can change the fader setting. If you're able to get the radio into a car that the Star computer can connect to, I think it can tell the radio its in a car other than, say an SLK. I don't think this has anything to do with whether there's a changer, or ipod, or whatever, connected to the radio.

I hope this makes sense.
Ray
www.perfectmarketaudio.com