Mercedes-Benz 2007 E -Class Wagon Operator's Manual page 206

Deactivating
Press button F or 1 again.
The indicator lamp on the button goes
out.
!
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 insuffi-
cient voltage in the battery. The system re-
sponds automatically by deactivating the rear
window defroster.
As soon as the battery has sufficient voltage, the
rear window defroster automatically turns itself
back on.
Controls in detail
Good visibility
205