See also:

Defrosting the windshield
You can use this function to defrost the windshield or to defrost the inside of the windshield and the side windows. You should only select the defrosting function until the windshield is clear ...

Activating/deactivating
WARNING Any accumulation of snow and ice should be removed from the rear window before driving. Visibility could otherwise be impaired, endangering you and others. The rear window defroster ...

Fuse box in the engine compartment
► Open the hood. Illustrated: GL 450 (GL 350 BlueTEC, GL 550 are similar) ► Remove any existing moisture from the fuse box using a dry cloth. ► To open: open clamps 2. ` ...