Function Of Rear Heated Seats - GF91.30-P-0005LF

Model 217

With Code 872 (Left and right rear seat heating)

Model 222

With Code 402 (Rear seat climate control)

Model 222

With Code 872 (Left and right rear seat heating)

Model 222

With Code P43 (Rear seat comfort package)

Courtesy of MERCEDES-BENZ USA

Shown on networking for model 222

Shown on networking for model 217

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Circuit 15R ON or circuit 15 ON

The electronic ignition lock control unit sends the status of circuit 15 via the interior CAN to the rear SAM control unit.

Seat heater (SIH), general

The seat heater enables the seat cushions and seat backrests to be heated in three heating levels. For vehicles with code P43 (Rear seat comfort package) or code 402 (Rear comfort seats, incl. seat heating and seat ventilation) and code 864 (Rear entertainment system), the heat output of the respective heater pads can be adjusted to the needs of the user. This means that the user can gradually set the distribution of the heat output of the heater pads via the remote control. The selected settings are displayed in the left rear display or right rear display.

Model 222

with code P43 (Rear seat comfort package)

Depending on the interior temperature, the heater pads are energized stronger than in a normal case and therefore heat up more quickly.

The lower the interior temperature, the stronger the supply to the heater pads.

The climate control, control unit sends the interior temperature value via the interior CAN to the rear SAM control unit.

The "fast seat heater" function can be activated or deactivated via the corresponding menu in the COMAND controller unit or the head unit.

The SIH function includes the following subfunctions:

SIH
Hot stone (model 222 With Code 406 (Multicontour seats in rear))
Distribution of backrest/seat cushion heat output (model 222 With Code P43 (Rear seat comfort package) or code 402 (Rear comfort seats, incl. seat heating and seat ventilation) and code 864 (Rear entertainment system))

SIH

The seat heater is switched on and off and the heat output is regulated (default status seat heater deactivated, all LEDs off) using the rear seat heater switch in the respective rear seat adjustment switch group or rear seat heater switch:

Actuating once: 3 LEDs illuminated, stage 3 of seat heater is activated (100 % heat output).
Actuating twice: 2 LEDs illuminated, stage 2 of seat heater is activated (65 % heat output).
Actuating three times: 1 LED lights up, level 1 of seat heater is activated (35 % heat output).
Actuating four times: All LEDs off, seat heater switched off.

If the seat heater is selected again with the same circuit status, heating level 3 is provided with only 90 % of the heat output. The heat output of the respective heating stages can be adjusted using a diagnostic tester.

Depending on the status of the seat heater, the rear SAM control unit sends status feedback for actuation of the LED in the respective seat heater switch via the interior CAN to the corresponding rear door control unit or rear control unit, which the LED actuates in the respective seat heater switch via the rear door LIN or rear LIN.

Seat heater actuation, left rear seat:

Model 222:

The left rear door control unit reads in the status of the left rear seat heater switch via the left rear door LIN and sends this via interior CAN to the rear SAM control unit.

Model 217:

The rear control unit reads in the status of the left rear seat heater switch via left rear LIN and sends this via interior CAN to the rear SAM control unit.

The rear SAM control unit assesses the status of the seat heater switch and, for vehicles with code 872 (Rear seat heater), a corresponding request to actuate the heater pads via heater LIN to the rear seat heater control unit.

For model 222 with code 402 (Rear comfort seats, incl. seat heating and seat ventilation), the rear SAM control unit sends a corresponding request to actuate the heater pads via interior CAN to the left rear control unit.

For model 222 with code P43 (Rear seat comfort package), the rear SAM control unit sends a corresponding request to actuate the heater pads via interior CAN, left rear seat control unit and left rear seat LIN to the left rear seat heater control unit.

Vehicles With Code 872 (Seat heater in rear):

The rear seat heater control unit actuates the following heater pads directly:

Left rear seat sitting surface heated cushion
Left rear backrest heated cushion

Model 222 With Code 402 (Rear comfort seats, incl. seat heating and seat ventilation):

The left rear seat control unit actuates the following heater pads directly:

Left rear seat sitting surface heated cushion
Left rear backrest heated cushion

Model 222 With Code P43 (Rear seat comfort package):

The left rear seat heater control unit actuates the following heater pads directly:

Left rear seat sitting surface heated cushion
Left rear backrest heated cushion

To monitor the seat heater, the left rear seat heater control unit reads in the signals of the heater pad temperature sensors directly.

The left rear seat control unit also actuates the following heater pads directly:

Seat cushion side bolster heater pad, left rear
Backrest side bolster heater pad, left rear

Right rear seat heater actuation:

Model 222:

The right rear door control unit reads in the status of the right rear seat heater switch via the right rear door LIN and sends this via interior CAN to the rear SAM control unit.

Model 217:

The rear control unit reads in the status of the right rear seat heater switch via right rear LIN and sends this via interior CAN to the rear SAM control unit.

For model 222 with code P43 (Rear seat comfort package), the rear SAM control unit sends a corresponding request to actuate the heater pads via interior CAN, right rear seat control unit and right rear seat LIN to the right rear seat heater control unit.

Vehicles With Code 872 (Seat heater in rear):

The rear seat heater control unit actuates the following heater pads directly:

Right rear seat sitting surface heated cushion
Right rear backrest heater pad

Model 222 With Code 402 (Rear comfort seats, incl. seat heating and seat ventilation):

The right rear seat control unit actuates the following heater pads directly:

Right rear seat sitting surface heated cushion
Right rear backrest heater pad

Model 222 With Code P43 (Rear seat comfort package):

The right rear seat heater control unit actuates the following heater pads directly:

Right rear seat sitting surface heated cushion
Right rear backrest heater pad

To monitor the seat heater, the right rear seat heater control unit reads in the signals of the heater pad temperature sensors directly.

The right rear seat control unit also actuates the following heater pads directly:

Seat cushion side bolster heater pad, right rear
Backrest side bolster heater pad, right rear

Function notes:

Then the seat heater is automatically switched off (timed). The timer control is realized by the rear SAM control unit.

Heating level 3 is activated for 8 min. Then the system automatically switches to heating stage 2.
Heating stage 2 is activated for 10 min. Then the system automatically switches to heating level 1.
Heating level 1 is active for 20 minutes. Then the seat heater is automatically switched off.

The timer control of the three heating stages can be adjusted using a diagnostic tester.

With circuit 50 ON, the power supply of the seat heater is interrupted for t = 20 s. This has no influence on the timer control and the actuation of the LEDs. No undervoltage is detected during startup.

Hot stone (model 222 With Code 406 (Multicontour seats in rear))

The hot stone function is a comfort function during which the seat heater is also switched on in addition to the massage function. The seat heater is switched on as long as the massage program is active.

The starting and ending of the massage function is performed via the remote control and is displayed in the left rear display or right rear display.

The left rear multicontour seat control unit or the right rear multicontour seat control unit sends the request to switch on the seat heater via interior CAN to the rear SAM control unit.

During the hot stone function, only the rear backrest heater pads are actuated. Information on the actuation of the heater pads can be found in the Seat Heater chapter.

The hot stone function can be parameterized using the diagnostic tester.

Shutoff criteria:

Switching off in event of error:
The rear seat control unit or the rear seat heater control unit are equipped with a protection relay that shuts off the earth supply to the respective heated cushion in the event of a fault. If the seat heater was switched off by one of the protection relays, the seat heater cannot be switched on again until another ignition cycle has taken place. The rear seat control unit or the rear seat heater control unit send corresponding messages via interior CAN to the rear SAM control unit.
Shutoff after circuit 15R OFF:
When switching from circuit 15R ON to circuit 15C ON, the timer control runs on for 5 minutes. If the circuit 15R is not switched back on within 5 minutes, the seat heater is reactivated.
Deactivation with undervoltage or overvoltage:
With undervoltage or overvoltage, the rear seat control units or rear seat heater control unit switch off the seat heater. The LEDs in the respective seat heater switch initially remain activated. If the on-board electrical system has been restored to normal voltage levels within 3 minutes, the seat heater starts again automatically.

However, if the shutoff lasts longer than 3 min, the LEDs in the respective seat heating switch are also switched off. If shutoff continues and the function is requested again by pressing the respective seat heater switch, the LEDs light up for 1.5 s and then go out.

In addition to the undervoltage or overvoltage protection that is integrated into the rear seat control units or the rear seat heater control unit, attention must also be paid to the voltage control of the energy management.
Switch off in event of voltage drop:
If one of the two supply lines of the rear seat control units or the rear seat heater control unit fails, the seat heater is switched off.
Deactivation in the event of excess temperature of the printed circuit boards in the respective control unit:
- At a printed circuit board temperature of more than 70°C, heating level 3 can no longer be activated.
- At a printed circuit board temperature of more than 80°C, heating level 3 and heating level 2 can no longer be activated.
- At a printed circuit board temperature of over 90°C, the seat heater can no longer be activated.
If no plausible printed circuit board temperature value is present, the interior temperature value is used instead. The climate control, control unit sends the interior temperature value via the interior CAN to the rear SAM control unit.
Shutoff in the event of a hardware defect:
If actuation of the heater pads is detected without a currently pending request from a seat heater switch, the power supply to the seat heater is switched off.
Deactivation in the event of "Time Out":
If the request is not received via interior CAN from the rear SAM control unit to actuate the seat heater, the seat heater is switched off.
Deactivation in the event of short circuit, overload or open circuit (line break):
The respective rear seat control unit or the rear seat heater control unit has detected a possible short circuit, overload or line break in the respective heater pad. The fault sources that have been listed can be diagnosed individually for each heater pad using a diagnostic tester.

Distribution of backrest/seat cushion heat output (model 222 With Code P43 (Rear seat comfort package) or code 402 (Rear comfort seats, incl. seat heating and seat ventilation) and code 864 (Rear entertainment system))

The heat output of the heater pads is configured menu-assisted via the remote control of the rear entertainment system.

The following heating elements can be activated or deactivated via the remote control:

Left rear seat sitting surface heated cushion
Left rear backrest heated cushion
Right rear seat sitting surface heated cushion
Right rear backrest heater pad

Operation takes place via the remote control and is shown in the left rear display or right rear display.

The remote control sends radio signals via the headphones antenna and remote control directly to the COMAND controller unit or the head unit. The COMAND controller or head unit sends the configuration information via user interface CAN, electronic ignition lock control unit and interior CAN to the rear SAM control unit, which processes and stores them.

At the same time, the COMAND controller unit or the head unit sends a switch-on request via telematics CAN to the left rear display or right rear display and the control signals via Media Oriented System Transport to the Rear Seat Entertainment system controller unit. The Rear Seat Entertainment system controller unit sends the picture data via LVDS line to the left rear display or right rear display.

Information on the actuation of the heater pads can be found in the Seat Heater chapter.

The heat output of the respective heater pads is listed in the following table, depending on the heating level.

Heating stage 1	Balance -3	Balance -2	Balance -1	Balance 0	Balance +1	Balance +2	Balance +3
Seat sitting surface heater pad	0 %	12 %	23 %	35 %	35 %	35 %	35 %
Backrest heater pad	35 %	35 %	35 %	35 %	23 %	12 %	0 %
Heating stage 2	Balance -3	Balance -2	Balance -1	Balance 0	Balance +1	Balance +2	Balance +3
Seat sitting surface heater pad	1 %	22 %	44 %	65 %	65 %	65 %	65 %
Backrest heater pad	65 %	65 %	65 %	65 %	44 %	22 %	1 %
Heating level 3	Balance -3	Balance -2	Balance -1	Balance 0	Balance +1	Balance +2	Balance +3
Seat sitting surface heater pad	1 %	34 %	67 %	100 %	100 %	100 %	100 %
Backrest heater pad	100 %	100 %	100 %	100 %	67 %	34 %	1 %

	Electrical function schematic, seat heater, rear seats		PE91.30-P-2055-97SEA
	Overview of system components of comfort heating systems		GF91.30-P-9990LF