GF91.30-P-0003RI Seat Heater (SIH), Function

GF91.30-P-0003RI Seat Heater (SIH), Function
- with CODE (873) Heated left and right front seats

General function requirements
^ C. 15R On

The circuit 15 status is transmitted by the EIS [EZS] control unit (N73) via interior CAN to the left front seat adjustment control unit with memory (N32/1) or right front seat adjustment control unit wit memory (N32/2).

Seat heaters, general
With the seat heater, it is possible to heat the seat cushions and the backrests of the front seats in three heating stages.

The seat heater comprises the following subfunctions:
^ Manual on/off function sequence
^ Automatic switch off function sequence

Manual on/off function sequence
The actuation of the seat heater stage 1 and 2 switch (S91/2s18) in the left seat adjustment switch group (S91/2) is read in by the left door control unit (N69/1).

The actuation of the seat heater stage 1 and 2 switch (S91/2s18) in the right seat adjustment switch group (S92/2) is read in by the right door control unit (N69/2).

The left door control unit or right door control unit transmits the request to the particular front seat adjustment control unit via the interior CAN.

The frequency used to press the seat heater switch determines the heat output of the seat heater:
Press once: Heating stage 2 (high heat output)
Press two times: Heating stage 1 (low heat output)
Press three times: Seat heater is switched off

The left front seat adjustment control unit actuates the following components:
- Left front seat heated cushion (R13/1)
- Left front backrest heated cushion (R13/2)

The front seat adjustment control unit actuates the following components:
- Right front seat cushion heater element (R13/3)
- Right front backrest seat cushion heater element (R13/4)

The heating stage that has been activated is indicated by red light-emitting diodes (LEDs) in the relevant seat heater switch.

When the seat ventilation is activated in vehicles with code (401) Front comfort seats, incl. seat heating and seat ventilation, heating stage 1 of the seat heater is not switched off until the seat ventilation is also switched off.

Automatic switch off function sequence
The period of time is controlled by the relevant front seat adjustment control unit:
- Heating stage 2 is active for t = 5 min.
Then the system automatically switches to heating stage 1.

- Heating stage 1 is active for t = 30 min.
Then the SIH is automatically switched off.

The period of time of the two heating stages is parameterizable via STAR DIAGNOSIS in the corresponding front seat adjustment control unit.

Other shutoff criteria:
- Shutoff after circuit 15R Off:
If circuit status circuit 15C is On, the timer control continues to run for t = 5 min. If circuit 15R is switched on again, then the seat heater is also switched on at the heating stage activated according to the timer control.

- Shutoff in the event of undervoltage or overvoltage:
In the event of undervoltage or overvoltage, the corresponding front seat adjustment control unit switches the seat heater off. The timer control continues to run. In the event of undervoltage, the LEDs in the seat heater switch are flashing. In the event of overvoltage, the LEDs are actuated continuously. If undervoltage is present for more than t > 30 s, a fault message is stored in the fault memory of the front seat adjustment control unit.

It is not possible to switch the seat heater on again until a permissible voltage is present.

- Shutoff during engine starting procedure:
When the engine is started, the seat heater is switched off. The timer control continues to run and the LEDs also continue to be actuated.

No undervoltage is detected during the starting procedure.

- Shutoff during seat adjustment:
The seat heater is switched off during an active seat adjustment. The timer control continues to run and the LEDs also continue to be actuated.

- Shutoff during Keyless-Go communication:
In vehicles with code (889) Keyless-Go, the seat heater is switched off during a search for the transmitter key (A8/1). The timer control continues to run and the LEDs also continue to be actuated.