Seat heater, function - GF91.30-P-0003RF
Model 205, 253 with code 401 (Climatised front seats)
Model 205, 253 with code 872 (Heated rear seats)
Model 205, 253 with code 873 (Seat heating for driver and front passenger)
Driver seat heater (with code 401 (Seat climate control for driver and front passenger) or with code 873 (Seat heater for driver and front passenger))
Front passenger seat heater (with code 401 (Seat climate control for driver and front passenger) or with code 873 (Seat heater for driver and front passenger))
Model 205
as of model year 2016
with code 401 (Climatised front seats)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
Model 205
as of model year 2016
with code 872 (Heated rear seats)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
Model 205
as of model year 2016
with code 873 (Seat heating for driver and front passenger)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
Model 253
with code 401 (Climatised front seats)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
Model 253
with code 872 (Heated rear seats)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
Model 253
with code 873 (Seat heating for driver and front passenger)
except code 221 (Electrically adjustable left driver seat)
except code 222 (Electrically adjustable right front seat)
except code 242 (Front passenger seat, electrically adjustable with memory function)
except code 275 (Memory package)
The front seat heater control unit in the front passenger seat replaces the driver seat heater control unit and the front passenger seat heater control unit with regard to its function. In the following text sections, only the term "seat heater control unit" is used.
Seat heater, rear seats (with CODE 872 (Seat heater in rear))
Function requirements, general
- Circuit 15R ON or circuit 15 ON
The electronic ignition lock control unit sends the status of circuit 15 over 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 stages. The master control unit for the seat heater function is the rear SAM control unit.
Model 205 (except 205.012/047/147/212/247)
with code 401 (Climatised front seats)
with code 577 (Remote activation of heating and ventilation systems)
Model 205 (except 205.012/047/147/212/247)
with code 577 (Remote activation of heating and ventilation systems)
with code 873 (Seat heating for driver and front passenger)
Model 205.012/047/147/212/247
with code 401 (Climatised front seats)
Model 205.012/047/147/212/247
with code 873 (Seat heating for driver and front passenger)
The pre-entry climate control function activates the seat heater for the driver seat for maximum t = 60 s after unlocking the vehicle. The driver seat is thereby preheated before the journey begins.
Function sequence for seat heater
The seat heater is switched on and off and the heat output regulated (default status seat heater deactivated, all LEDs off) via the front seat heater switch in the respective seat climate control switch group or via the respective rear seat heater button:
- Press once: 3 LEDs illuminate, stage 3 of seat heater activated (P = 100%).
- Press twice: 2 LEDs illuminate, stage 2 of seat heater activated (P = 65%).
- Press three times: 1 LED lights up, stage 1 of seat heater activated (P = 35%).
- Press four times: All LEDs off, seat heater switched off.
If, with an unchanged circuit status, the front seat heater switch (with code 401 (Seat climate control for driver and front passenger) or with code 873 (Seat heater for driver and front passenger)) or the rear seat heater button (with code 872 (Seat heater in rear)) is operated again, only P = 90% of the heater output is made available for heating level 3. The heat output of the respective heating levels can be adjusted in the factory using a diagnostic tester.
Function sequence for driver seat heater (with code 401 (Seat climate control for driver and front passenger) or with code 873 (Seat heater for driver and front passenger)):
The left front door control unit reads in the status of the left front seat heater switch over the left front door LIN and sends it over the interior CAN to the rear SAM control unit. The rear SAM control unit evaluates this and sends a corresponding request depending on the equipment via one of the following connections:
- Via interior CAN to the driver seat control unit (with CODE 275 (Memory package))
- Over the heater LIN to the driver seat control unit (with CODE 221 (Left electrically adjustable driver seat))
- Via the heater LIN to the seat heater control unit (except code 275 (Memory package) and except code 221 (Left electrically adjustable driver seat))
The driver seat control unit or the seat heater control unit then actuates the following heater pads directly
- Left front seat cushion heater pad
- Left front seat backrest heater pad
- Heater pad for adjustable seat cushion length, left front seat (with CODE 275 (Memory package) or with CODE 221 (Left electrically adjustable driver seat))
The driver seat control unit or the seat heater control unit continuously checks the function of all seat heater components involved and sends the corresponding status via one of the following connections, depending on the equipment:
- Via heater LIN to the rear SAM control unit (except CODE 275 (Memory package))
- Via interior CAN to the rear SAM control unit (with CODE 275 (Memory package))
In accordance with the frequency with which the left front seat heater switch is operated, the rear SAM control unit sends the status of the seat heater via the interior CAN, left front door control unit and left front door LIN to the driver seat climate control switch group, which then actuates the LEDs in the left front seat heater switch correspondingly.
Function sequence for front passenger seat heater (with code 401 (Seat climate control for driver and front passenger) or with code 873 (Seat heater for driver and front passenger)):
The right front door control unit reads in the status of the right front seat heater switch over the right front door LIN, and sends it over the interior CAN to the rear SAM control unit. The rear SAM control unit evaluates this and sends a corresponding request depending on the equipment via one of the following connections:
- Over the interior CAN to the front passenger seat control unit (with CODE 242 (Electrically adjustable front passenger seat with memory function))
- Over the heater LIN to the front passenger seat control unit (with CODE 222 (Electrically adjustable right front seat))
- Via heater LIN to the seat heater control unit (except code 242 (Electrically adjustable front passenger seat with memory function) and except code 222 (Right electrically adjustable front seat))
The front passenger seat control unit or the seat heater control unit then actuates the following heater pads directly:
- Right front seat cushion heater pad
- Right front seat backrest heater pad
- Heater pad for adjustable seat cushion length, right front seat (with CODE 242 (Electrically adjustable front passenger seat with memory function) or with CODE 222 (Electrically adjustable right front seat))
The front passenger seat control unit or the seat heater control unit continuously checks the function of all seat heater components involved and sends the corresponding status via one of the following connections, depending on the equipment:
- Over the heater LIN to the rear SAM control unit (except CODE 242 (Electrically adjustable front passenger seat with memory function))
- Over the interior CAN to the rear SAM control unit (with CODE 242 (Electrically adjustable front passenger seat with memory function))
In accordance with the frequency with which the right front seat heater switch is operated, the rear SAM control unit sends the status of the seat heater via the interior CAN, right front door control unit and right front door LIN to the front passenger seat climate control switch group, which then actuates the LEDs in the right front seat heater switch correspondingly.
Function sequence for the rear seat heater (with CODE 872 (Seat heater in rear)):
The left rear door control unit or the right rear door control unit reads in the status of the respective rear seat heater button via the door LIN and sends this via the interior CAN to the rear SAM control unit. The rear SAM control unit evaluates this and sends the corresponding request via the heater LIN to the rear seat heater control unit.
The rear seat heater control unit then actuates the following heater pads directly:
Left rear seat:
- Left rear seat sitting surface heated cushion
- Left rear backrest heated cushion
Right rear seat:
- Right rear seat sitting surface heated cushion
- Right rear backrest heater pad
The rear seat heater control unit continuously checks the operative function of all involved components of the seat heater and sends the corresponding status via the heater LIN to the rear SAM control unit. According to the frequency with which the respective rear seat heater button is pressed, the rear SAM control unit sends the status of the seat heater via the interior CAN, rear door control unit, and rear door LIN to the rear seat heater button. The LEDs in the rear seat heater button are actuated accordingly.
Function note:
Then the seat heater is automatically switched off (timed). The timer control is realized by the rear SAM control unit.
- Heating level 3 is active for t = 8 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 level 1 is active for t = 20 min. Then the seat heater is automatically switched off.
The timer control of the three heating levels can be adjusted via the diagnostic tester in the rear SAM control unit.
Shut off criteria
If one of the following criteria occurs, the seat heater is switched off automatically:
- Shutoff in the event of a hardware defect:
If the seat heater control unit, driver seat control unit, front passenger seat control unit or the rear seat heater control unit reports an active actuation of the heater pads to the rear SAM control unit although no request by a seat heater switch or a seat heater button is pending, the power supply of the heater pads is switched off via an integrated protection relay in the seat heater control unit, the driver seat control unit, front passenger seat control unit or in the rear seat heater control unit by the rear SAM control unit.
- Deactivation in the event of excess temperature of the printed circuit boards in the respective control unit
- Heating stage 3 can no longer be activated if the PCB temperature is T > 70°C.
- Heating stage 3 and heating stage 2 can no longer be activated if the PCB temperature is T > 80°C.
- The seat heater can no longer be activated if the PCB temperature is T > 90°C.
If no circuit board temperature value is present, the interior temperature value is assessed instead. The climate control control unit sends the interior temperature value over the interior CAN to the rear SAM control unit.
If the PCB temperature reaches T > 90°C, a fault message is stored in the fault memory. Manual switch on requires a cooling down of T = 2°C for the corresponding temperature threshold.
- Shutoff in the event of an error (short circuit, overload or open circuit (line break)):
The respective control unit detects a possible short circuit, overload or a line break in the respective heater pad and deactivates the power supply. The fault sources that have been listed can be diagnosed individually for each heater pad using a diagnostic tester.
- Shutoff during engine starting procedure:
When the engine is started (cold start), the seat heater is deactivated for t = 20 s. During a hot start, the seat heater is deactivated for t = 3 to 5 s. The timer control continues to run, and the LEDs remain switched on. No undervoltage is detected during startup.
- Switching off by energy management:
In order to prevent the battery from discharging in all driving cycle phases, the state of charge is continuously evaluated. Depending on the situation, the HS [SIH] are also deactivated.
If the seat heater is switched off, the LEDs initially remain switched on. If the on-board electrical system reaches its on-board electrical system voltage again within the next t = 3 min, the seat heater function is automatically activated. If the shutoff lasts longer than t = 3 minutes, the LEDs are also switched off. If the shutoff continues and the function is requested again, the LEDs illuminate for t = 1.5 s and then extinguish.
- Shutoff in the event of voltage loss:
If one of the two supply lines (circuit 30 or circuit 30g) of the respective control unit fails, the seat heater is switched off.
- Shutoff after circuit 15R OFF:
With circuit 15R OFF and circuit 15C ON, timer control runs on for t = 5 min. If circuit 15R is switched on again, the seat heater is also switched on again.
- Shutoff in the event of "Timeout error":
If the request of the rear SAM control unit for actuating the seat ventilation is discontinued or a "Timeout period" from the electronic ignition lock control unit is recognized, the seat heater is switched off.
- Shutoff at end of diagnosis:
After the diagnosis has finished, the seat heater switches off.
| Electrical function schematic, seat heater, rear seats | Model 205, 253 with code 872 (Heated rear seats) | PE91.30-P-2055-97FBA | |
| Electrical function schematic, seat heater, front | Model 205, 253 with code 401 (Climatised front seats) Model 205, 253 with code 873 (Seat heating for driver and front passenger) | PE91.30-P-2056-97FBA | |
| Overview of system components of comfort heating systems | GF91.30-P-9990RF |