Heated seats switch-off function

P91.30-2128-05

N22 AAC control and operating module (for Code (581a) automatic air conditioning)

N22/7 Comfort AAC control and operating module (for Code (581b) comfort automatic air conditioning)

N72/1 Upper control panel control module

N72/1s10 Left front HS/seat ventilation switch

N72/1s11 Right front HS/seat ventilation switch

N73 DI control module

R13/1 Left front seat heated cushion

R13/2 Left front backrest heated cushion

R13/3 Right front seat heated cushion

R13/4 Right front backrest heated cushion

CAN B CAN class B

Function requirement:

 Circuit 15R ON or circuit 15 ON

 No undervoltage

 The seat heater is switched on

Manual switch-off (example: heated seats, left)

The switch-off process is initiated on the left front HS/seat ventilation switch (N72/1s10) by processing the corresponding applied position, heating stage 1 or 2.

The upper control panel control module (N72/1) then interrupts the circuit of the left front seat heated cushion (R13/1) and left front backrest heated cushion (R13/2).

At the same time the LEDs in the left front HS/seat ventilation switch (N72/1s10) go out.

Switch off the heated seats during the starting procedure

During the starting procedure the current supply to the left front seat heated cushion (R13/1) and left front backrest heated cushion (R13/2) or the right front seat heated cushion (R13/3) and right front backrest heated cushion (R13/4) is switched off.

 The timer control continues to run.

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Automatic switch-off at ignition (circuit 15C) OFF

The switch-off process is initiated by turning back using the transmitter key to circuit 15C. The upper control panel control module (N72/1) then interrupts the circuit to the left front seat heated cushion (R13/1) and left front backrest heated cushion (R13/2) or the right front seat heated cushion (R13/3) and right front backrest heated cushion (R13/4). At the same time the LEDs in the left front HS/seat ventilation switch (N72/1s10) or in the right front HS/seat ventilation switch (N72/1s11) go out.

 The internal time procedure of the heated seats continues to run for a period of 5 minutes. This means that if, within these five minutes, circuit 15R at least is switched on, then the heated seats continue to run without any additional actuation of the left front HS/seat ventilation switch (N72/1s10) or right front HS/seat ventilation switch (N72/1s11).

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Automatic switch-off at battery voltage  11 V

The upper control panel control module (N72/1) recognizes the undervoltage (undervoltage given for longer than 3 s) and automatically triggers the heated seats switch-off procedure to protect the battery. The upper control panel control module (N72/1) then interrupts the heated cushion circuit.

If an undervoltage is detected each of the active LEDs flashes at a frequency of 1.5 Hz.

If the undervoltage is present for longer than 30 s, then an error is filed in the memory.

 The battery voltage transmitted by the electronic ignition switch control module (N73) serves as the basis for the voltage detection.

Automatic switching off of the heated seats (timer control)

The upper control panel control module (N72/1) implements the timer control for the heated seats.

After switching on stage 2 this remains ON for a period of

5 min. Then it switches automatically to stage 1.

After switching on stage 1 this remains ON for a period of

20 min. Then the heated seats switch off.

 The heating times can be programmed via the diagnosis; the times listed in the table are ex-factory settings.

Automatic switch-off at excess temperature

The upper control panel control module (N72/1) receives the message of the interior temperature from the AAC control and operating module (N22) or the comfort AAC control and operating module (N22/7). If an interior temperature of more than 30 °C is received, the switched-on heated seats are switched off.

At switch off due to excess temperature, the LEDs retain their status. Thus, for example, actuation of the excess temperature switch-off can only be determined by the lack of heating effect in the seat.

Interruption detection

In order to prevent the heated seats from being activated in the event that a plug is dropped or if a line breaks, then in a 10 ms cycle the applied resistance value is checked at the driver stage output on the upper control panel control module (N72/1).

As long as the heated seats are not active, the electronics circuit checks whether the heated cushion is connected. If an interruption is present for longer than 2.5 s, then the corresponding fault bit is set and the heated seats can no longer be activated, until the interruption has been rectified.