2005 Mercedes C-Class Owner's Manual - Page 175

Controls in detail Good visibility Rear window defroster The rear window defroster uses a large amount of power. To keep the battery drain to a minimum, switch off the defroster as soon as the rear window is clear. The defroster is automatically deactivated after approximately 6 to 17 minutes of operation depending on the outside temperature. Activating Press button F in the climate control panel ( page 175). The indicator lamp on the button comes on. Deactivating Press button F again. The indicator lamp on the button goes out. Warning! G Any accumulation of snow and ice should be removed from the rear window before driving. Visibility could otherwise be impaired, endangering you and others. ! If the rear window defroster switches off too soon and the indicator lamp starts flashing, this means that too many electrical consumers are operating simultaneously and there is insufficient voltage in the battery. The system responds automatically by deactivating the rear window defroster. As soon as the battery has sufficient voltage, the rear window defroster automatically turns itself back on. 173