Switching off with switch, function

P67.29-2014-01

S21e2 Rear window defroster indicator lamp

S21s9 Rear window defroster switch

Function survey

When switched on the rear window defroster can be switched off with the rear window defroster switch (S21s9).

To switch off, the rear window defroster switch (S21s9) connects the corresponding input on the extended activity module (EAM) (N10/1) to ground for a short time. The extended activity module (EAM) (N10/1) evaluates this information and switches off the rear window defroster relay (F1k1) and the rear window defroster indicator lamp (S21e2) by disconnecting the ground connection.

-----------------------------------------------------------------------------------------


The rear window defroster relay (F1k1) and the rear window defroster indicator lamp (S21e2) are connected directly to the extended activity module (EAM) (N10/1) via their own lines.

If the rear window defroster relay (F1k1) is switched off circuit 30 on the antenna splitter (A2/5) is interrupted thereby interrupting the current through the rear window defroster (R1).

-----------------------------------------------------------------------------------------

The rear window defroster switches also off without manual operation if:

 the voltage is too low for a period of min. 30 seconds,

 a crash is recognized by the traction systems control module (N2/7) and transmitted from there to the all-activity module (AAM) (N10) or

 if the set switch-on time dependent on the outside temperature and the speed has expired.


If the voltage is too low for a short time the rear window defroster indicator lamp (S21e2) flashes. Heating current cannot flow through the rear window defroster while the lamp is flashing.