Active Seat Ventilation

Active Seat Ventilation

Active seat ventilation
The active seat ventilation enables individual cooling of the seat cushions and backrests.
the optional extra (optional extra 453) "active seat ventilation, front" is available for the driver's and passenger's seat.
Nine fans are fitted in each seat.
The fans are distributed as follows:
- 5 fans in the seat cushion
- 4 fans in the backrest







Brief description of components
The following components are described:
- SMFA and SMBF: driver seat module and passenger seat module
- Button for active seat ventilation

SMFA and SMBF: driver seat module and passenger seat module
The seat module activates the fans in the seat cushion and in the backrest. The fans are supplied with voltage by the seat module. The seat module activates the function display of the button for the active seat ventilation (an LED in the left-hand button and right-hand button in the IHKA operating unit). The seat module is connected on the K-CAN (body CAN).







Button for active seat ventilation
The button for the active seat ventilation is installed in the IHKA operating unit / control unit. The button signals for the active seat ventilation are processed in the IHKA control unit.
The first press of the button for active seat ventilation switches on ventilation stage 3. Further button pressures switch on the next-lowest ventilation stage or switch off the active seat ventilation.
If the button for active seat ventilation is pressed for longer than 1.2 seconds, the active seat ventilation switches off.
The IHKA control unit converts the button signal for the active seat ventilation into a digital signal.
The IHKA control unit sends the signal as a message on the K-CAN (body CAN).







System functions
The following system functions are described:
- Activation of the fan settings
- Deactivation with undervoltage and overvoltage

Activation of the fan settings
The active seat ventilation can be switched on as of terminal 15 On.
The parallel switched fans have the status "OFF" and 2 speed stages (high and low).
Depending on the selected ventilation stage, the driver seat module (SMFA) or passenger seat module (SMBF) controls 2 speed stages for the fans as follows.







After an operating period of 15 minutes, the system switches back automatically from ventilation stage 3 to ventilation stage 2.
When the ignition is switched off briefly (terminal 15 "OFF" for less than 15 minutes), the function status of the active seat ventilation is retained.
This means: If the active seat ventilation was switched on before terminal 15 "OFF", it switches on again automatically at terminal 15 "ON".
Each fan has a control / diagnosis lead in addition to the power supply.
The speed stages of the fans are activated and the fans are monitored via this control / diagnosis lead.
The total output of all fans is 24 Watts or briefly (starting output max. 5 minutes) 30 Watts.

Shutdown by the energy management
The energy management in the vehicle can briefly switch off the active seat ventilation depending on the energy balance. However, the function display is retained.
The energy management ensures that there is always sufficient starter motor current.
The energy management monitors the vehicle even with the engine at a standstill.
The energy management system comprises all components in the vehicle which generate, store and consume energy. The data for the energy management is distributed across a number of control units (e.g. CAS, JBE and DME/DDE).

Deactivation with undervoltage and overvoltage
The driver seat module (SMFA) or passenger seat module (SMBF) detect undervoltage and overvoltage. The seat module switches off the fans for the active seat ventilation.
Conditions for the shutdown:
- Undervoltage: On-board supply voltage less than 9 volts
- Overvoltage: on-board supply voltage greater than 16 Volts

Notes for Service department

General information
The optional extra 453 "active seat ventilation, front" is only provided together with the optional extra 456 "comfort seat, front, electrically adjustable".

No liability can be accepted for printing or other errors. Subject to changes of a technical nature