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If you are referring to the actual controller in the dash, it is available seperately. There is a special tool (sheetmetal "keys") that are used to remove it. You should be able to buy both the control unit and the "keys" at this website (the "fastlane" and "partsShop" keys at the top of the MercedesShop home screen will direct you the proper area of this site. I understand the prices are quite competitive. I work at a dealership, so I don't have any first-hand experience buying here. Give them a try, or else your local dealership can help you also. If it seems like the button or buttons are mechanically defective, then replacement will be about the only cure.