Electric seat ventilation, function - GF91.30-P-0002RF

Model 205, 253 with code 401 (Climatised front seats) 

Driver seat ventilation 

Front passenger seat ventilation 

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 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)

The front seat heater control unit in the front passenger seat functionally replaces the driver seat heater control unit and the front passenger seat heater control unit. In the following sections, only the term "seat heater control unit" is used.

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 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 function.

Model 205, 253

with code 401 (Climatised front seats)

with code 889 (KEYLESS-GO)

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

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 205.012/047/147/212/247

with code 401 (Climatised front seats)

The pre-entry climate control function activates the seat ventilation for the driver seat for maximum t = 60 s after unlocking the vehicle. The driver seat is thus cooled before departure.

Seat ventilation function sequence 

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 one time: 3 LEDs light up, stage 3 of seat ventilation or seat cooling activated (P = 100%).

  First the seat ventilation motors are activated in the "suction" direction of rotation (seat cooling); after t = 10 min the direction of rotation is reversed to "blowing" (seat ventilation).

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

Function sequence for driver seat ventilation: 

The left front door control unit reads in the status of the left front seat ventilation switch via the left front door LIN and sends it to the rear SAM control unit via interior CAN. 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 directly actuates the following motor groups:

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

The driver seat control unit or the seat heater control unit continuously checks the function of all components involved in the seat ventilation and sends the corresponding status, depending on the vehicle's equipment, via one of the following connections:

• 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))

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 driver seat climate control switch group, which actuates the LED in the left front seat ventilation switch accordingly.

Function sequence for front passenger seat ventilation: 

The right front door control unit reads in the status of the right front seat ventilation switch via the right front door LIN and sends this to the rear SAM control unit via interior CAN. 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 the 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 directly actuates the following motor groups:

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

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

• 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 ventilation switch is operated, the rear SAM control unit sends the status of the seat ventilation 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 LED in the right front seat ventilation switch correspondingly.

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 v = 6 km/h. As of v > 9 km/h, the original stage set 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 t = 7 min after the respective seat ventilation has been switched on with the engine running.

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 t = 8 min. Then it switches automatically to stage 2.
• Seat ventilation stage 2 is active for t = 10 min. Then it switches automatically to stage 1.
• Seat ventilation stage 1 is active for t = 20 min. Then seat ventilation is automatically switched off.

The timer control of the three 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 ventilation is switched off automatically:

• Shutoff in the event of a hardware defect: 

  If the seat heater control unit, the driver seat control unit or the front passenger seat control unit signals active actuation of the seat ventilation motors to the rear SAM control unit, even though no request exists from a seat ventilation switch, the power supply to the seat ventilation motors is switched off through an integrated protection relay in the seat heater control unit, driver seat control unit or in the front passenger seat control unit by the rear SAM control unit.

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

  The seat heater control unit, the driver seat control unit or the front passenger seat control unit detects a possible short circuit, overload or line break in the respective seat ventilation motor and deactivates the power supply. The fault sources that have been listed can be diagnosed individually for each seat ventilation motor using a diagnostic tester.

• Shutoff during engine starting procedure: 

  When the engine is started (cold start), the seat ventilation is deactivated for t = 20 s. During a hot start, the seat ventilation is deactivated for t = 3 to 5 s. The timer control continues to run, and the LEDs remain switched on. No undervoltage assessment takes place 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 seat ventilation is also deactivated if necessary.

  If the seat ventilation is switched off, the LEDs in the respective seat ventilation button remain on initially. If the on-board electrical system reaches its on-board electrical system voltage again within the next t = 3 min, the seat ventilation function is automatically activated. If the shutoff lasts longer than t = 3 min, the LEDs of the relevant seat ventilation switch are also switched off. If shutoff continues and the function is requested again by pressing the respective seat ventilation switch, the LEDs light up for t = 1.5 s and then go out.

• Shutoff in the event of voltage loss: 

  If one of the two supply lines (circuit 30 or circuit 30g) of the seat heater control unit, the driver seat control unit or the front passenger seat control unit fails, the seat ventilation 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 ventilation 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 ventilation is switched off.

• Shutoff at end of diagnosis: 

  After the diagnosis has finished, the seat ventilation switches off.

	Seat ventilation electrical function schematic		PE91.30-P-2053-97FBA
	Overview of system components of comfort heating systems		GF91.30-P-9990RF