Interior - Rear Seat Ventilation Is Weak Or Inoperative
SI B52 13 10
Seats
November 2010
Technical Service
SUBJECT
Rear Seat Ventilation Is Perceived as Weak or Not Working
MODEL
F01, F02, F04 (7 Series)
F07 (550i Gran Turismo)
Vehicles equipped with SA 454 (Rear Ventilated Seats)
SITUATION
With the rear seat ventilation switched on, the customer perceives that the ventilation (air flow) is weak or not working at all.
CAUSE
In most cases, the rear seat ventilation is working properly. The design and function of the rear seat ventilation is a further development of the
system used in the previous 7 Series (E65/66), and should not be compared to in regards to function and operation. An intelligent temperature
control has been incorporated for enhanced comfort. The functional description of the rear seat ventilation operation in this bulletin will be
integrated into a future ISTA (Integrated Service Technical Application) version.
INFORMATION
Functional Description and Operating Information;
1. The ventilation of each seat is individually adjustable. Each seat consists of the following components:
^ 2 radial fans (one for each seat and backrest, fitted on the insulation box under the front edge of the seat cushion; the backrest fan in the F07 is
located on the backrest rear panel).
^ 2 ventilation mats (one for each seat cushion and backrest on the foam section)
^ 2 NTC (Negative Temperature Coefficient) temperature sensors (seat and backrest)
2010 BMW 750i xDrive AWD (F01) V8-4.4L Turbo (N63) Page 369
2. The ventilated rear seats are equipped with a temperature control. This controls the fan output and fan speed according to the set temperature. The
seat bottom and backrest are each controlled separately (similar to the logic of seat heating).
^ Setting 1: Slightly cool
^ Setting 2: Medium
^ Setting 3: Cold
3. When switching down from setting 3 to 2 or from 2 to 1, and if the seat ventilation was active for longer than 1 minute, the seat ventilation is
switched off briefly for a fixed amount of time. The seat ventilation then continues to run at the temperature-regulated state at the nominal
temperatures for that specific setting.
4. After switching on setting 3, it runs for a fixed time at 100% PWM (Pulse Width Modulated) speed. After this time, the seat continues to run at
the temperature-regulated state at the nominal temperatures for that specific setting.
5. If the ventilated seat is active when the MAX AC function is switched on (only in vehicles equipped with 4-zone air-conditioning system), the seat
setting is switched automatically to setting 3. When MAX AC is switched off, the system is adjusted to the previously selected setting again.
6. If seat heating and seat ventilation are running at the same time, the ventilated seat is operated at a fixed fan speed for that specific setting. The
temperature control is not active for as long as the seat heating is active (seat heating and seat ventilation use the same temperature sensor).
7. For acoustic masking, the permissible fan speed is limited by vehicle speed and the fan output of the ventilation system. The function is designed
so that even at speeds used in city traffic or at medium fan speeds, there is no longer any limit on fan speed. However, when the vehicle is stationary
and with automatic heating and air-conditioning switched off, noise disturbance to passengers is avoided by limiting the fan speed.
