Front Seat Heating, Checking
Components Which Participate in the Activation of the Front Seat Heating
The control head, the Climatronic Control Module -J255-, sends the request to switch on the seat heating via the data bus to the respective control module (the control module depends on the vehicle version and vehicle equipment level). Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function and to the appropriate WIRING DIAGRAM.
- In the case of vehicles without a Memory Seat/Steering Column Adjustment Control Module -J136- and a Front Passenger Memory Seat Control Module -J521-, the Vehicle Electrical System Control Module -J519- activates the driver seat heating and front passenger seat heating. The Climatronic Control Module -J255- control head, first sends the request for seat heating activation via the data bus to the Data Bus On Board Diagnostic Interface -J533- and then to the Vehicle Electrical System Control Module -J519-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function andto the appropriate WIRING DIAGRAM (for the particular vehicle system).
- In the case of vehicles with a Memory Seat/Steering Column Adjustment Control Module -J136- and a Front Passenger Memory Seat Control Module -J521-, the Memory Seat/Steering Column Adjustment Control Module -J136- activates the driver seat heating and the Front Passenger Memory Seat Control Module -J521- the front passenger seat heating. The Climatronic Control Module -J255- control head, first sends the request for seat heating activation via the data bus to the Data Bus On Board Diagnostic Interface -J533- and then to the Memory Seat/Steering Column Adjustment Control Module -J136- and the Front Passenger Memory Seat Control Module -J521-. If only a -J136- and no Front Passenger Memory Seat Control Module -J521- is installed in a vehicle, the Memory Seat/Steering Column Adjustment Control Module -J136- activates the driver seat heating, and the front passenger seat heating is then activated by the Vehicle Electrical System Control Module -J519-. Refer to 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 seat heating is switched off while the stop function is active (to protect the Battery -A-). The setting for the activation of the heated seats remains stored, however, in the Climatronic Control Module -J255- control head. After the engine was started again via the start function, the seat heating is switched on again. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- The set driver seat heating 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 heating 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 heating activation is erased. Refer to the Owner's Manual.
- Depending on the vehicle, the seat heating setting automatically reduces after a certain amount of time (for example, after 10 minutes). Refer to the Owner's Manual.
Seat heating activation can differ, depending on the vehicle version. Refer to the appropriate WIRING DIAGRAM.
Depending on the vehicle version and equipment, the various information regarding seat heating 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. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If there is a condition, where the heating of the driver or passenger seat cannot be switched on (for example due to a short circuit in the connection to a seat heater element 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 heating, first check the event memory of the control modules activating the seat heating.
The function test of seat heating 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) 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 heating 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 heating level setting has been selected. The seat heating, the actual and target seat temperature, the actual current supplied to the seat heating, 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 heating 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 heating is switched on, the function indicator lamps in the buttons illuminate. Refer to the Vehicle Owner's Manual.
- The seat heating 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 heating 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 heating can differ with the same setting on the Climatronic Control Module -J255-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.