Seat ventilation, rear seats

The seat ventilation enables individual cooling of the seat cushions and the backrests.

Brief description of components

Seat module, rear driver's side / rear passenger side

The seat modules are fitted in the luggage compartment.

The seat modules are networked with the vehicle via the CAN BUS.

Rear centre console switch centre

The control unit rear centre console switch centre has the following functions:

• CAN BUS interface to the vehicle electrical system
  
• Interface to the seat switches
  

The control unit rear centre console switch centre is fitted in the rear centre armrest.

Operating switch rear driver's side / rear passenger side

Depending on the equipment, various switch blocks are fitted.

The switch blocks are connected by means of ribbon cables to the rear centre console switch centre (BZMF).

Fan motors

Each seat contains 8 or 9 fan motors (depending on seat version).

Main functions

Seat ventilation

The desired fan output can be set via the operating switch. The three LEDs indicate the corresponding fan stage.

• The fan command is transferred from the switch block to the BZMF across a ribbon cable.
  
• The BZMF sends the message across the K-CAN SYSTEM to the Car Access System (CAS).
  
• The CAS as ”gateway control unit” passes the message on to the corresponding seat module via the K-CAN PERIPHERALS.
  
• The seat module activates the fan motors directly.
  

Activation of the fan motors

The relevant seat module activates the fan motors. The fan motors:

• are switched on by activating the voltage supply
  
• can be activated separately for backrest and seat cushion
  
• can be operated 2 speed stages
  
• signal any standstill to the diagnosis.
  

For each fan motor, the power supply is supplemented by a control / diagnosis lead. Via the control / diagnosis lead:

• the speed stage is activated
  
• the fan motors are monitored.
  

Operation

The seat ventilation is active as of terminal 15. Stage 3 is switched on with the first press of the button. Pressing the button again selects the next lowest stage or ”off”. If the button is pressed for longer than 1.2 seconds, the seat ventilation switches off.

If the ignition is switched off briefly, the function mode of the seat ventilation is retained. The seat ventilation is active again in the corresponding stage when the ignition is switched on again.

Switch activation stage - fan blower speed

After an operation period of 15 minutes, the system switches automatically from Stage 3 back to Stage 2.

Safety function

Consumer shutdown

In the case of signal ”Control peak reduction priority” from the power module, the power of the seat ventilation is reduced or it is switched off.

The function indicators (LEDs) remain switched on when the seat ventilation is switched off for a brief period.