See also:

Problems with the rear window defroster
The rear window defroster has deactivated itself prematurely or cannot be activated. Switch off any consumers that are not required, e.g. reading lamps or interior lighting. When the battery ...

Cleaning the exterior lighting
  Clean the plastic lenses of the exterior lights with a wet sponge and a mild cleaning agent, e.g. Mercedes-Benz car shampoo or cleaning cloths. Only use cleaning agents or cleaning ...

Function restrictions
For safety reasons, some COMAND functions are restricted or unavailable while the vehicle is in motion. You will notice this, for example, because you will either not be able to select certain ...