Front Heated Seats Function - GF91.30-P-0004GR

MODEL 166 up to model year 2016 with CODE 401 (Front deluxe seats, incl. seat heating and seat ventilation) 

MODEL 166 up to model year 2016 with CODE 873 (Heated left and right front seats) 

Function requirements, general 

• Circuit 15R ON

The electronic ignition lock control unit transmits the terminal status 15 via the interior CAN.

Seat heaters, general 

The seat heater enables the seat cushions and backrests of the front seats to be heated in three heater stages.

The seat heater function comprises the following partial functions:

• Function sequence for manually switching on/off 
• Function sequence for automatic switch off 

Function sequence for manually switching on/off 

Operation takes place via the left front seat heater button and the right front seat heater button in the upper control panel control unit.

The requests from the seat heater buttons are read in by the upper control panel control unit and transmitted via battery sensor LIN to the SAM control unit.

On vehicles with CODE 275 (Memory package (driver seat, steering column, mirror)), these requests are forwarded by the SAM control unit via interior CAN to the driver seat control unit or the front passenger seat control unit.

On vehicles except CODE 275 (Memory package (driver seat, steering column, mirror)), these requests are forwarded by the SAM control unit via center console switch LIN to the driver seat control unit or the front passenger seat control unit.

The driver seat control unit actuates the following heater pads:

• Left front seat sitting surface heated cushion
• Left front backrest heated cushion

The front passenger seat control unit actuates the following heater pads:

• Right front seat sitting surface heated cushion
• Right front backrest heated cushion

The heat output depends on the heating level that has been selected using the seat heater button. The particular heating level that has been activated is indicated via red LEDs in the particular seat heater button.

• Pressing once: Heating stage 3 (100% heat output, three LEDs light up)
• Pressing twice: Heating stage 2 (70% heat output, two LEDs light up)
• Pressing three times: Heating stage 1 (40% heat output, one LED lights up)
• Pressing four times: Seat heater is switched off (no LEDs light up)

If the seat heater is selected again with the same circuit status, heating stage 3 is provided with only 90% of the heat output.

When the seat ventilation is activated on 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.

Function sequence for automatic switch off 

The driver seat control unit or the front passenger seat control unit is responsible for the timer control.

• Heating level 3 is active for t = 8 min.

  Then the system automatically switches to heating stage 2.

• Heating level 2 is active for t = 10 min.

  Then the system automatically switches to heating level 1.

• Heating level 1 is active for t = 20 min.

The seat heater is then automatically switched off.

The time settings for the three heating levels can be adjusted via the diagnostic tester in the driver seat control unit or in the front passenger seat control unit.

Other shutoff criteria:

• Shutoff after circuit 15R OFF:

  If circuit 15C remains ON, the timer control runs on for t = 5 min. If circuit 15R is switched on again, then the seat heater is also activated at the heating stage in line with the timer control.

• Shutoff during engine starting procedure:

  The timer control continues to run, and the LEDs remain switched on. No undervoltage is detected during startup.

• Shutoff in the event of a hardware defect:

  If actuation of the heater pads is detected without a request from a seat heater button, the power supply to the seat heater is switched off.

• Deactivation with undervoltage or overvoltage:

  If the driver seat control unit or the front passenger seat control unit switches off the seat heater, the LED for the respective seat heater button remains switched on at first. If the on-board electrical system reaches its normal voltage within the next t = 3 min., the seat heater function is automatically reactivated.

  However, if the shutoff lasts longer than t = 3 min, the LED of the relevant seat heater button is also switched off.

  If the shutoff continues and the function is requested again via the respective seat heater button, the LED comes on for t = 1.5 s and then goes off.

• Shutoff for overtemperature of PCBs in driver seat control unit or in front passenger seat control unit:

  Heating stage 3 can no longer be activated if the PCB temperature is T < 90 °C.

  Heating stage 3 and heating stage 2 can no longer be activated if the PCB temperature is T < 100 °C.

  The seat heater can no longer be activated if the PCB temperature is T < 110 °C.

  If no plausible circuit board temperature value is available, the interior temperature value is used instead.

	Electrical function schematic, seat heater, front		PE91.30-P-2056-97NAA
	Overview of system components of comfort heating systems		GF91.30-P-9990GR