Multicontour seat control unit (MCS), component description - GF91.25-P-5201LEA
MODEL 221.0 /1 with CODE (406) Rear multicontour seat as of model year 2009 /YoM 08
Shown on model 221.0 model year 2009 / YoM 08
Location
The left and right rear multicontour backrest is located in direction of travel in the trunk behind the paneling.
Tasks
- Inflation and deflation of the multicontour backrest in accordance with the requests issued by the driver or front passenger
- Actuation of massage function
- Communication via interior CAN (CAN B) with rear seat control unit (N25/6)
- Adjustment of seat hardness and seat contour
- Actuation of pressure regulating valves in backrest for lumbar support, lateral support and the valves in the massage insert
- Actuation of the multicontour seat pneumatic pump (M40)
- Adjusting the stored pressure values when calling up the memory feature and storing the actual contours
These are grouped as follows:
- Reading in of sensors and signals
- Evaluation of input factors
- Actuation of components
Reading in of sensors and signals
These input factors are read in via the following connections:
- Direct line
- Interior CAN
Direct line
- Circuit 30
- Tml. 31
- Piezo sensors in the pressure sensor valves for measurement of the air pressure in the individual air cushions of the seat backrest contour insert
Interior CAN
The left and right rear multicontour backrest communicates via the interior CAN with:
- the rear seat control unit; adjustment and storage of seat contours
- the multicontour seat pneumatic pump for actuation of compressed air supply
- the central gateway control unit (N93) as router for signals from:
- the ESP control unit (N47-5); for the PRE-SAFE function
- RCP control unit (N72/2) via the telematics CAN (CAN A) and COMAND control unit (A40/3) for the adjustment functions
Evaluation of input factors
The read in input factors are evaluated by the rear multicontour backrest control unit. Actuation of the air cushions in the seat is performed via a piezo valve integrated into the multicontour insert, which is then actuated by the multicontour backrest control unit via direct lines with 220 V DC.
Actuation of components
The actuation of the components takes place via the following connections:
- Direct line
- Interior CAN
Direct line
The following components are actuated via direct lines:
- Piezo valves in pressure sensor valves for actuation of air pressure in the individual air cushions of the multicontour seat contour insert
- Piezo valves in massage insert for actuation of massage function
Interior CAN
The rear multicontour backrest control unit communicates via the interior CAN with:
- the multicontour seat pneumatic pump for actuation of compressed air supply
- the central gateway control unit as router for signals via the COMAND control unit for display functions and feedback signals to the rear control panel control unit
Design
The rear multicontour backrest control unit contains not only the intelligent circuit but also output stages. These are used to transform voltage from 12 V to 220 V direct current. The rear multicontour backrest control unit also includes a safety circuit. It switches itself off automatically if an output stage is defective. It is also equipped with a high-voltage safeguard, which only switches on the high voltage when each connector on the rear multicontour backrest control unit is plugged in.
The 6-pin plug is used to connect the rear multicontour backrest control unit to the interior CAN and the power supply.
The 28-pin plug is used to connect the rear multicontour backrest control unit to the piezo sensors and piezo valves in the pressure sensor valves of the contour insert and the piezo valves in the backrest massage insert
Function
Short-term control
The short-term control is actuated following each adjustment process (manual adjustment, memory request, initialization) for a certain period of time. It compensates for excess pressure deviations from the specified pressure of each air cushion (cushion areas, connected to a pressure sensor, are jointly in the temporary control phase) within a parameterized time period. Vacuum deviations during this phase are not compensated for. This phase is used to immediately compensate for large pressure jumps when sitting down and leaning back in a comfort-oriented fashion.
Long-term control
After the short-term control, the long-term control becomes active for the active cushions, until it is reset by events with a higher priority. Almost without the customer noticing, the lumbar support is regulated in the specified time frame such that the mean value of the actual pressure adjusts to the specified pressure within the repeatability over a certain period of time.
If an adjustment to the specified pressure cannot be achieved in several consecutive steps, a "gross leak" is detected. The affected cushion area is deactivated completely until the malfunction is no longer present.
Non-active air cushions are deflated in increments to a pressure less than the minimum pressure.
Variants
There is only one variant of multicontour backrest unit hardware available which is included in the package contents of the various software variants:
- Software for front multicontour backrest (only model year 2009 / YoM 08)
- Software for front dynamic multicontour seat control unit with dynamic function and with massage function (only model year 2009 /YoM 08)
- Rear multicontour backrest control unit
The assignment for driver, front passenger seat and the country or left-hand/right-hand drive vehicle assignment is also coded by the software.
| Left rear multicontour backrest control unit wiring diagram | Control unit N32/20 | PE91.25-P-2110-99SAA | |
| Right rear multicontour backrest control unit wiring diagram | Control unit N32/21 | PE91.25-P-2120-99SAA |