Electric Seat Ventilation, Function - GF91.30-P-0002FR

Model 257, 290 up to Model year 2021 with code 401 (Climatised front seats) 

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 ventilation, general 

The seat cushions and backrests can be ventilated in three stages using the seat ventilation. The rear SAM control unit is the master control unit for the seat ventilation.

The seat ventilation at the front passenger side can also be operated via the left front seat climate control switch group.

Model 257, 290

up to Model year 2021

with code 401 (Climatised front seats)

with code 889 (KEYLESS-GO)

For comfort opening of the vehicle, the seat ventilation motors of the driver seat are first actuated in the "suction" direction of rotation (seat cooling). If circuit 15R is then not switched on within 5 minutes or the vehicle is locked again, the seat ventilation is switched off.

The seat ventilation includes the following subfunctions:

• Switch seat ventilation on and off 
• Seat ventilation 
• Switching off automatically 

Switch seat ventilation on and off 

The seat ventilation is switched on and off and the ventilation output regulated (output state of seat ventilation deactivated, all LEDs off) using the seat ventilation switch in the respective switch group, seat climate control:

• Press once: 3 LEDs light up, stage 3 of the seat ventilation is activated (100 % output).

  First, the seat ventilation motors are actuated in the "suction" direction of rotation (seat cooling), and after 10 minutes the direction of rotation is reversed to "blowing" (seat ventilation).

• Press twice: 2 LEDs light up, stage 2 of the seat ventilation is activated (65 % output).
• Press three times: 1 LED lights up, stage 1 of the seat ventilation activated (P = 35 % output).
• Press four times: All LEDs off, the seat ventilation is switched off.

Function note 

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

• Seat ventilation stage 3 is active for 8 minutes. Then it switches automatically to stage 2.
• Seat ventilation stage 2 is active for 10 minutes. It then switches automatically to stage 1.
• Seat ventilation stage 1 is active for 20 minutes. Then seat ventilation is automatically switched off.

The timer control can be adjusted through the diagnostic tester in the rear SAM control unit.

Seat ventilation 

Driver seat ventilation 

The left front door control unit reads in the status of the left front seat ventilation switch via left front door LIN and sends a corresponding request to the rear SAM control unit via interior CAN. The rear SAM control unit evaluates this and sends the request to switch on the seat ventilation depending on the equipment involved over the following connection:

• Over the interior CAN to the driver's seat control unit (with code 278 (Fully electric front seats) or code 275 (Memory Package))
• Over the heater LIN to the front seat ventilation control unit (except code 278 (Fully electric front seats) and except code 275 (Memory Package))

The driver's seat control unit or the front seat ventilation control unit then actuates the following motor groups directly:

• Left front seat cushion seat ventilation motors
• Left front backrest seat ventilation motors

The driver's seat control unit or the front seat ventilation control unit continuously checks the function of all the components involved in the seat ventilation and sends the corresponding status depending on the vehicle's equipment over the following connection:

• Over the interior CAN to the rear SAM control unit (with code 278 (Fully electric front seats) or code 275 (Memory Package))
• Over the heater LIN to the rear SAM control unit (except code 278 (Fully electric front seats) and except code 275 (Memory Package))

Corresponding to the actuation frequency of the left front seat ventilation switch, the rear SAM control unit sends the status of the seat ventilation via interior CAN, left front door control unit and left front door LIN to the left front seat climate control switch group, which actuates the LEDs in the left front seat ventilation switch accordingly.

Front passenger seat ventilation 

The right front door control unit reads in the status of the right front seat ventilation switch via right front door LIN and sends a corresponding request to the rear SAM control unit via interior CAN. The rear SAM control unit evaluates this and sends the request to switch on the seat ventilation, depending on the equipment involved, over the following connection:

• Over the interior CAN to the front passenger seat control unit (with code 278 (Fully electric front seats) or code 275 (Memory Package))
• Over the heater LIN to the front seat ventilation control unit (except code 278 (Fully electric front seats) and except code 275 (Memory Package))

The front passenger seat control unit or the front seat ventilation control unit then actuates the following motor groups directly:

• Right front seat cushion seat ventilation motors
• Right front backrest seat ventilation motors

The front passenger's seat control unit or the front seat ventilation control unit continuously checks the function of all the components involved in the seat ventilation and sends the corresponding status, depending on the vehicle's equipment, over the following connection:

• Over the interior CAN to the rear SAM control unit (with code 278 (Fully electric front seats) or code 275 (Memory Package))
• Over the heater LIN to the rear SAM control unit (except code 278 (Fully electric front seats) and except code 275 (Memory Package))

Corresponding to the actuation frequency of the right front seat ventilation switch, the rear SAM control unit sends the status of the seat ventilation via interior CAN, right front door control unit and right front door LIN to the right front seat climate control switch group, which actuates the LEDs in the right front seat ventilation switch accordingly.

Reduction of noise level 

In order to reduce the noise level of the seat ventilation when the vehicle is stationary, it is shifted down to level 1 if the vehicle speed drops below 6 km/h. As of 9 km/h, the originally selected stage is activated. The instrument cluster sends the vehicle speed via user interface CAN, electronic ignition lock control unit and interior CAN to the rear SAM control unit. The noise level reduction does not become active until 7 minutes after the respective seat ventilation has been switched on for the first time with the engine running.

Switching off automatically 

The seat ventilation is switched off automatically if one of the following events occurs:

• Shut-off in the event of a hardware defect 

  If there is no corresponding request for an active actuation the seat ventilation is switched off.

• Shutoff in the event of a fault (short circuit, overload or line break) 

  In the event of a short circuit, an overload or a line break, the power supply of the identified seat ventilation motor is switched off. The exact source of the fault can be diagnosed using the diagnostic tester.

• Shutoff when the engine starts 

  When the engine is started (cold start), the seat ventilation is switched off for 20 s. During a warm start, the seat ventilation is switched off for 3 to 5 s. The timer control continues to run, and the LEDs in the respective seat ventilation switch remain switched on. No undervoltage assessment takes place during startup.

• Switching off by means of energy management 

  To prevent a battery from discharging, the state of charge is continuously evaluated. Depending on the situation, the seat ventilation is also switched off if necessary.

  If the seat ventilation is switched off, the LEDs in the respective seat ventilation switch remain on initially. If the on-board electrical system reaches the specified voltage again within the following 3 minutes, the seat ventilation starts again automatically. If the shutoff lasts longer than 3 min, the LEDs in the respective seat ventilation switch are also switched off. If shutoff continues and the seat ventilation is requested again by pressing the respective seat ventilation switch, the LEDs light up for 1.5 s and then go out.

• Shutoff at voltage drop 

  The seat ventilation is switched off in the event of a voltage drop.

• Shutoff after circuit 15R OFF 

  For circuit 15R OFF and circuit 15C ON, the timer control runs on for another 5 minutes. If circuit 15R is switched on again, the seat ventilation is also switched on again.

• Shut-off in the event of "Timeout error" 

  If the electronic ignition lock control unit detects a timeout error, the seat ventilation is switched off.

• Shutoff at end of diagnosis 

  The seat ventilation is switched off after diagnosis has been completed.

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