Front Seat Ventilation, Checking
Components Which Participate in the Activation of the Front Seat Heating and Ventilation
The control head, the Climatronic Control Module -J255-, sends the request to switch on the seat ventilation via the data bus to the respective control module (the control module depends on the vehicle version and vehicle equipment level). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function and to the appropriate WIRING DIAGRAM.
- A Memory Seat/Steering Column Adjustment Control Module -J136- and a Front Passenger Memory Seat Control Module -J521- are always installed in vehicles with seat ventilation. This control module switches the seat ventilation on. Activation is performed as in vehicles with only seat heating in which the Memory Seat/Steering Column Adjustment Control Module -J136- and the Front Passenger Memory Seat Control Module -J521- are installed. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function and to the appropriate WIRING DIAGRAM (for the particular vehicle system).
- A start-stop system is available for certain engines for this vehicle. For vehicles with a Start/Stop System, the ventilation can be switched off for the time in which the stop function is active (to protect the Battery -A-). The setting for the activation of the seat ventilation remains stored, however, in the Climatronic Control Module -J255- control head. After the engine was started again via the start function, the seat ventilation is switched on again. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- The set driver seat ventilation stage can be stored in a key-dependent manner. The settings made prior to the ignition being switched off are applied during the next driving cycle. Refer to Operating Instructions.
- On vehicles without the passenger occupant detection system for the front passenger and rear seats, there is currently no automatic shut-off for the seat ventilation if there is an unoccupied seat while driving. If the ignition is turned off and not turned on again within approximately 10 minutes, the setting for the seat ventilation activation is erased. Refer to the Owner's Manual.
- Depending on the vehicle, the seat ventilation setting automatically reduces after a certain amount of time (for example, after 10 minutes). Refer to the Owner's Manual.
Seat ventilation activation can differ, depending on the vehicle version. Refer to to the appropriate WIRING DIAGRAM.
Depending on the vehicle version and equipment, the various information regarding seat ventilation activation (the setting transmitted by the Climatronic Control Module -J255- control head, the target and actual temperature of the seat, etc.) is displayed in different measured value blocks in various control modules. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If there is a condition, where the ventilation of the driver or passenger seat cannot be switched on (for example due to a short circuit or an interruption in the current supply to the respective control unit, etc.), this will be stored as a malfunction in the Vehicle Electrical System Control Module -J519-, in the Memory Seat/Steering Column Adjustment Control Module -J136- or in Front Passenger Seat Heating Control Module -J521- (depending on the vehicle type and the vehicle equipment level). For this vehicle, information stating that the Diagnostic Trouble Code (DTC) memory in the relevant control module must to be read out may not be sent via the data bus to the Climatronic Control Module -J255- control head. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function. In the event of a complaint regarding seat ventilation, first check the event memory of the control modules activating the seat ventilation.
The function test of seat ventilation activation is described in the Guided Fault Finding for each control module (Vehicle Electrical System Control Module -J519-, Memory Seat/Steering Column Adjustment Control Module -J136- or Front Passenger Memory Seat Control Module -J521-, depending on the vehicle version and equipment). Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If, for example, the voltage at terminal "30" measured at the Vehicle Electrical System Control Module -J519- falls below a value stored in the Vehicle Electrical System Control Module -J519-, the seat ventilation output is reduced or switched off completely in order to reduce the load of the Generator -C-. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
In the "read measured values" function of the Guided Fault Finding, the Climatronic Control Module -J255- control head displays which seat ventilation level setting has been selected. The seat ventilation, the actual and target seat temperature, the actual current supplied to the seat ventilation, etc. are displayed as a function of the version and equipment of the vehicle in the "read measured values" function of the relevant control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
Depending on the vehicle version, the front passenger seat ventilation can switch off after a certain period of time when it is detected that the seat is not occupied (deactivation via the passenger occupant detection system is not planned for the start of production, introduction not yet finalized). Refer to the Operating instructions.
- There are different versions of the Climatronic Control Module -J255- control head. Refer to the parts information. The different versions can be recognized, for example, by the symbols on the buttons -2 and 3- (for vehicles equipped with "seat heating") and -1 and 4- (vehicles with "seat heating/seat ventilation").
- When the seat ventilation is switched on, the function indicator lamps in the buttons illuminate. Refer to the Vehicle Owner's Manual.
- The seat ventilation setting is adjusted by the Climatronic Control Module -J255- control head. The setting is transmitted to the relevant control module via the data bus. The target temperatures for the different seat ventilation settings are stored in the relevant control modules. Depending on the version of the control module and the vehicle production period, the target temperature for the seat ventilation can differ with the same setting on the Climatronic Control Module -J255-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
Note the Following When Operating the Seat Ventilation
- In this vehicle, heating is not automatically performed in the seat ventilation mode (activation and deactivation via the -1 and 4- buttons). Seat heating is only activated when seat heating is switched on via the -2 and 3- buttons. As a result, the following operating modes are possible (seat heating without seat ventilation, seat ventilation without seat heating, and seat heating with seat ventilation). Refer to the Operating Instructions.
- The blower activation for the seat cushion and seat backrest (for example 1 blowers each in the seat backrest and seat cushion of each seat) depends on the seat ventilation setting (approximately 40% of the maximum output at setting 1, and approximately 85% at setting 3). Use the Vehicle Diagnostic Tester in the "Guided Fault Funding" function.
- The selected setting for the driver seat ventilation is saved when the ignition is switched off and the selected setting is allocated via the ignition key. After the ignition is switched on/the engine is started, the seat ventilation are activated according to the last setting. Refer to the Operating Instructions.
- The selected setting for the front passenger seat and rear seat ventilation is also stored when the ignition is switched off. However, if the ignition remains off for longer than approximately 10 minutes, the seat ventilation are not reactivated after the ignition is switched on/the engine is started (the settings are erased). Refer to the Operating Instructions.