Comfort heater function - GF91.30-P-0001CE
MODEL 204.0 /2 with CODE (873) Heated left and right front seats as of model year 2009 /YoM 08
MODEL 204.3 with CODE (873) Left and right front seat heaters
MODEL 204.9 with CODE (873) Left and right front seat heaters
Seat heaters, general
The seat heater (SIH) function enables the seat cushions and backrests of the front seats to be heated.
The seat heater function is made up of the following subfunctions:
- Function sequence for manual on/off
- Function sequence for automatic switch off
Manual on/off function sequence
Operation takes place via the left front seat heater button and the right front seat heater button in the upper control panel control unit.
Seat heater button requests are read in by the upper control panel control unit and sent over the instrument panel LIN to the front SAM control unit. This routes the requests over the interior CAN to the rear SAM control unit.
The following heater pads are actuated by the rear SAM control unit as requested:
- Left front seat sitting surface heated cushion
- Left front backrest heated cushion
- Right front seat sitting surface heated cushion
- Right front backrest heated cushion
The heat output is dependent on the heating stage chosen on the seat heater button and each activated heating stage is indicated by red LEDs in the corresponding seat heater button:
Press once: Heating stage 3 (100 % heat output, 3 LEDs)
Press two times: Heating stage 2 (70 % heat output, 2 LEDs)
Press three times: Heating stage 1 (40 % heat output, 1 LED)
Press four times: Seat heater switched off (no LED)
Function sequence for automatic switch off
The rear SAM control unit is responsible for the seat heater timer control.
- 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.
The seat heater is then automatically switched off.
The timer settings of the heating stages can be programmed in the rear SAM control unit using the diagnosis tester.
Other shutoff criteria:
- Shut-off after circuit 15R Off:
After circuit 15R is switched 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 is switched on again, then the seat heater is also activated at the heating stage in line with the timer control.
This circuit status is read in by the electronic ignition lock control unit and forwarded via the interior CAN to the rear SAM control unit.
- Switching off when starting engine:
The timer control for the seat heater continues to run, the LEDs in the seat heater button remain on.
- Switching off at undervoltage or overvoltage:
If an undervoltage or overvoltage is detected in the on-board electrical system, the rear SAM control unit switches off the seat heater's power supply. The LEDs in the seat heater button remain on. If the on-board electrical system returns to its normal voltage level within t = 3 min, the seat heater is switched on again.
If the undervoltage or overvoltage lasts for longer than t = 3 min, the LEDs in the seat heater button are switched off. If the seat heater function is requested again when an undervoltage or overvoltage is present, the LEDs in the seat heater button light up for t = 1.5 s and then go off again.
- Switching off in the event of defective hardware:
If an actuation of the heater pads by the seat heater button is detected without any request pending, the power supply for the seat heater is switched off.
- Switching off in the event of overtemperature.
- At an interior temperature of T > 42°C heating stage 3 for the seat heater can no longer be activated.
- At an interior temperature of T > 45°C heating stage 3 and heating stage 2 in the seat heater can no longer be activated.
- At an interior temperature of T > 55°C the seat heater cannot be activated at all anymore.
The current value of the interior temperature is recorded by the interior temperature sensor and read in by the automatic air conditioning control and operating unit. This routes information over the interior CAN to the rear SAM control unit.
If no plausible interior temperature value is present, the outside temperature value is used instead.
| Electrical function schematic, seat heater (SIH) | PE91.30-P-2050-97FAB | ||
| Overview of comfort heater system components | GF91.30-P-9990CE |