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

GF91.30-P-0003GM Seat Heater (SIH), Function
- with CODE (872) Electrically heated left and right rear seats
- with CODE (873) Heated left and right front seats
- with CODE (401) Front comfort seats, including seat heating and seat ventilation

General function requirements
^ C. 15R On

Seat heaters, general
The seat cushions and the backrests of the front seats can be heated by the seat heater.

In addition, heating of the left and right seats in the 2nd seat row is possible for code (872) Electric seat heater for left and right rear seat.

The seat heater consists of the following subfunctions:
^ Function sequence for manually switching the front seat heater on and off
^ Function sequence for manually switching the rear seat heater on and off (with code (872) Electrically heated left and right rear seats)
^ Automatic switch off function sequence

Function sequence for manually switching the front seat heater on and off
Operation takes place via the left front seat heater switch
(N72/1s10) and the right front seat heater switch (N72/1s11) in the upper control panel control unit (N72/1). The requests from the seat heater switch are relayed to the front SAM control unit (N10) by the upper control panel control unit via the interior CAN.

The front SAM control unit actuates the following heated cushions:
- Left front seat heated cushion (R13/1)
- Left front backrest heated cushion (R13/2)
- Right front seat cushion heater element (R13/3)
- Right front backrest seat cushion heater element (R13/4)

The heat output depends on the heating stage that has been selected using the seat heater switch:
Press once: Heating stage 3 (100 % heat output)
Press two times: Heating stage 2 (60 % heat output)
Press three times: Heating stage 1 (30 % heat output)
Operate four times: Seat heater is switched off

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

Function sequence for manually switching the rear seat heater on and off
Operation takes place via the left seat heater switch, 2nd seat row (N72/2s10) and the right seat heater switch, 2nd seat row (N72/2s11) in the rear control panel control unit (N72/2). The requests that are read in are sent by the rear control panel control unit to the seat heater, seat ventilation and steering wheel heater control unit (N25/7) via the interior CAN.

The seat heater, seat ventilation and steering wheel heater control unit actuates the following heated cushions:
- Left 2nd row seat heated cushion (R13/5)
- Left 2nd row backrest heated cushion (R13/6)
- Right 2nd row seat heated cushion (R13/7)
- Left 2nd row backrest heated cushion (R13/8)

The heat output depends on the heating stage that has been selected using the seat heater switch:
Press once: Heating stage 3 (100 % heat output)
Press two times: Heating stage 2 (60 % heat output)
Press three times: Heating stage 1 (30 % heat output)
Operate four times: Seat heater is switched off

The heat output of heating stage 3 is only 100 % when it is activated for the first time during a driving cycle. For every subsequent activation the heat output is limited to 90 %. A driving cycle ends when the transmitter key is removed (A8/1).

Automatic switch off function sequence
The timer control of the front seat heater is carried out by the front SAM control unit and the timer control of the rear seat heater is carried out by the seat heater, seat ventilation and steering wheel heater control unit.

The following heating times are programmed in the manufacturer default setting:
- Heating stage 3 is active for t = 5 min.
Then the system automatically switches to heating stage 2.

- Heating stage 2 is active for t = 10 min.
Then the system automatically switches to heating stage 1.

- Heating stage 1 is active for t = 20 min.
Then the SIH is automatically switched off.

The time settings of the individual heating stages can be programmed using STAR DIAGNOSIS.

Other shutoff criteria:
- Cutout in the event of a hardware fault:
If actuation of the heater pads is detected without a current request from a seat heater switch, the power supply to the seat heater is switched off. Any timer control or function indicator that may be active is also shut off. A fault is also stored in the fault memory of the relevant control unit.

- Cutout due to undervoltage:
If the voltage drops below U = 10.0 V for longer than t ≥ 2 s, the seat heater is switched off and the timer control continues to run.

If undervoltage is detected, the active LEDs in the left front seat heater switch and the right front seat heater switch flash at a frequency of approx. 1.5 Hz and with a brightness of 50 %. The seat heater cannot be switched on again until a permissible voltage of U = 11.0 V has been present for longer than t = 3 seconds.

- Cutout due to overvoltage
If the voltage exceeds U = 15.5 V, the seat heater is switched off. The timer control continues to run. The active LEDs are actuated in flashing mode. The seat heater cannot be switched on again until a voltage of U ≤ 15.0 V is present.

- Cutout after circuit 15R Off:
When circuit 15R switches off, the seat heater is also switched off. However, the timer control continues to run for t = 5 min, as long as circuit 15C is on.

If circuit 15R or circuit 15 are switched on again, then the seat heater is also activated at the heating stage in line with the timer control.