Rear Defroster
Thread Starter
Super Member
Joined: Aug 2013
Posts: 530
Likes: 21
From: ATL
2023 S580 (Current) 2011 S550
Rear Defroster
The light on the dash button works, but I dont think the rear defroster is working. I sometimes see condensation/fogging at the bottom of rear window and it doesn't go away when I hit the button.
Hd
Hd
Senior Member
Joined: Nov 2002
Posts: 303
Likes: 25
Does it only seem to happen when it's very cold out - but eventually defrosts? From the climate control engineering notes on the W221 series:
The rear window heater does not switch on immediately after actuation of the corresponding switch on the AC operating unit at extremely low outside temperatures. In order to provide the best possible window deicing performance, the rear window heater is only activated above a certain interior temperature when outside temperatures are extremely cold. However, the function LED in the operating unit lights up immediately the button is pressed. Similarly the heating duration of the rear window heater (automatic shutoff) can vary depending on the outside temperature and other ambient conditions. These control features are intentional. Please explain this logic to the customer. Replacing parts does not remedy the problem.
