Switching on, function

P67.29-2014-01

S21e2 Rear window defroster indicator lamp

S21s9 Heated rear window switch

Function sequence

The rear window heater can be switched on under the following preconditions:

 Circuit 61 ON (engine running recognition)

 No undervoltage

The availability of circuit 61 is placed on the engine compartment CAN by the instrument cluster (A1) as circuit 61e information and read out by the Extended Activity module (EAM) (N10/1). The circuit 61e guarantees the availability of a minimum engine speed and

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the presence of the charging voltage. The circuit 61e is thus a certain criteria for the engine running recognition.

The heated rear window switch (S21s9) is read in and evaluated directly by the Extended Activity module (EAM) (N10/1). When switching on, the input of N10/1 is briefly connected to ground. The N10/1 then switches the ground to the heated rear window indicator lamp (S21e2) and the coil in the heated rear window relay (F1k1).

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The heated rear window indicator lamp (S21e2) and the heated rear window relay (F1k1) are actuated by the Extended Activity module (EAM) (N10/1) via separate lines.

The heated rear window relay (F1k1) connects circuit 30 to the antenna splitter (A2/5). The antenna splitter (A2/5) then supplies the heated rear window (R1) with electric heating current.

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The Extended Activity module (EAM) (N10/1) also checks the occurrence of a present undervoltage.