Electric seat ventilation, function

P91.30-2483-82

Function requirements, general

 Circuit 15R ON

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

Seat ventilation, general

The seat cushions and backrests of the front seats can be ventilated in three stages using the seat ventilation.

 During comfort opening of the vehicle, the seat ventilation of the driver seat is switched on in stage 3. If circuit 15R is not switched on at this time, the seat ventilation is switched off after t = 5 min.
Detailed information about the comfort opening function can be found in the separate "Function description for theft protection and locking" function description in subfunction "Convenience feature (CF [KFB])".

The electric seat ventilation function encompasses the following subfunctions:

 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 ventilation button and the right front seat ventilation button in the upper control panel control unit.

The requests from the seat ventilation 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, mirrors)), 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 motor groups:

 Left front seat cushion seat ventilation motors

 Left front backrest seat ventilation motors

The front passenger seat control unit actuates the following motor groups:

 Right front seat cushion seat ventilation motors

 Right front backrest seat ventilation motors

The seat ventilation depends on the ventilation stage selected using the seat ventilation button. The particular ventilation stage that has been activated is indicated via red LEDs in the particular seat ventilation button.

 Pressing once: 3 LEDs light up, ventilation stage 3 activated

 Pressing twice : 2 LEDs light up, ventilation stage 2 activated

 Pressing three times: 1 LED lights up, ventilation stage 1 activated

 Pressing four times: All LEDs off, seat ventilation switched off

Function sequence for automatic switch off

If one of the following criteria occurs, the seat ventilation is switched off automatically:

 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, the seat ventilation is also switched on in the previously activated ventilation stage.

 Deactivation with undervoltage or overvoltage:

If the driver seat control unit or the front passenger seat control unit switches off the seat ventilation motors, the LED for the respective seat ventilation button initially goes on. If the on-board electrical system reaches its normal voltage again within the next t = 3 min, the seat ventilation function is automatically reactivated.

However, if the shutoff lasts longer than t = 3 min, the LED in the respective seat ventilation button is also switched off.

It the shutoff procedure continues and the function is requested again for the corresponding seat ventilation button, the LED comes on for t = 1.5 s and then goes out.

 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 seat ventilation is also deactivated if necessary.

 Shutoff during engine starting procedure:

During a start sequence, only the seat ventilation motors are switched off. The LEDs of the respective seat ventilation button continue to be lit. Undervoltage is not evaluated while starting and no faults are stored.