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Checking air conditioner components on vehicles with a high-voltage system > < Checking of heated rear windowZ1

A4 Mk3

Checking of front seat heating and ventilation
Checking of front seat heating and ventilation
Components involved in the seat heating and ventilation actuation process
The air conditioner operating and display unit, Climatronic control unit -J255- transmits the request for activation of the seat heating/seat ventilation by way of the data bus to the appropriate control unit (the control unit depends on the vehicle model and equipment → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 for the relevant control unit).
t  On vehicles with no seat and steering column adjustment control unit with memory -J136-, the onboard supply control unit -J519- actuates the driver side seat heating directly. If fitted, the seat ventilation is actuated via the control unit for front left seat ventilation -J800- by -J519- (different assignment of measured value blocks in -J519-).
t  On vehicles with no front passenger seat adjustment with memory control unit -J521-, the onboard supply control unit -J519- actuates the passenger side seat heating directly. If fitted, the seat ventilation is actuated via the control unit for front right seat ventilation -J799- by -J519- (different assignment of measured value blocks in -J519-).
t  On vehicles with a driver seat with easy entry facility and/or with memory function, the seat and steering column adjustment control unit with memory -J136- actuates the driver side seat heating and (if fitted) the seat ventilation directly (different assignment of measured value blocks in -J519-).
t  On vehicles with a passenger seat with electric easy entry facility, the front passenger seat adjustment with memory control unit -J521- actuates the passenger side seat heating.
t  As of Model Year 2010 a start/stop system will be available as an optional extra for this vehicle in conjunction with certain engines. On vehicles with a start/stop system, the seat heating and ventilation are deactivated whilst the stop function is active (to protect the battery -A-). The setting for actuation of the heated seats (and the seat ventilation) is however retained in the operating and display unit, Climatronic control unit -J255-. Once the engine has been re-started via the start function, the seat heating (and ventilation) are activated again → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
  Note
t  The control unit for front right seat ventilation -J799- and the control unit for front left seat ventilation -J800- are actuated by the onboard supply control unit -J519- by way of a local data bus → Current flow diagrams, Electrical fault finding and Fitting locations.
t  Actuation of the seat heating and seat ventilation may be different for the Audi A5 and the Audi A4 → Current flow diagrams, Electrical fault finding and Fitting locations.
t  The various items of information on actuation of the seat heating and ventilation (the setting transmitted by the air conditioner operating and display unit, Climatronic control unit -J255-, the specified and actual seat temperature, etc.) are displayed in different measured value blocks of the onboard supply control unit -J519- and/or the seat and steering column adjustment control unit with memory -J136- depending on the vehicle model and equipment → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
t  Situations preventing activation of the driver's/front passenger's seat heating or ventilation (e.g. short circuit in connection to seat heating element, open circuit in power supply to corresponding control unit) are stored as faults in the onboard supply control unit -J519-, the seat and steering column adjustment control unit with memory -J136- or the front passenger seat adjustment with memory control unit -J521- (depending on the vehicle model and equipment). On this vehicle, no information is currently transmitted via the data bus to the air conditioner operating and display unit, Climatronic control unit -J255- indicating that the event recorder in the corresponding control unit or in the convenience system central control unit -J393- has to be read out → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051. In the event of problems with seat heating or ventilation, the first step should therefore always be to read out the event recorders of the control units which actuate the seat heating and ventilation.
t  Checking actuation of the heated seats and seat ventilation is described in the guided fault-finding routine for the corresponding control unit (onboard supply control unit -J519-, seat and steering column adjustment control unit with memory -J136- or front passenger seat adjustment with memory control unit -J521-, depending on vehicle model and equipment) → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
t  If, for example, the voltage measured at the onboard supply control unit -J519- at terminal „30“ drops below a value stored in the onboard supply control unit -J519-, the seat heating and ventilation power is reduced or the function is completely deactivated to relieve the load on the alternator -C- → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
t  The seat heating/ventilation setting is displayed in the measured value block of the air conditioner operating and display unit, Climatronic control unit -J255-. Actuation of the seat heating and seat ventilation, as well as the actual and specified temperatures in the seat and the actual current flowing via the seat heating etc. are displayed in the applicable control unit depending on the vehicle model and equipment, e.g. in the measured value block of the onboard supply control unit -J519- → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
t  Depending on the vehicle model, heating or ventilation of the front passenger's seat may be deactivated after a certain period if the system detects that this seat is not occupied → Owner's manual.
   
t  There are different versions of the air conditioner operating and display unit, Climatronic control unit -J255- → Electronic parts catalogue. The different versions can be recognised for example from the symbols on the buttons -A- (for vehicles with „Seat heating“ optional extra) and -B- (for vehicles with „Seat heating/seat ventilation“ optional extra).
t  This illustration shows the air conditioner operating and display unit, Climatronic control unit -J255- in the „Deluxe“ version fitted as of the start of production.
t  As of Model Year 2012, modified -J255- are to be gradually introduced (introduction depending on model and version). Pay attention to the correct assignment → Electronic parts catalogue.
  A87-10587
t  The modifications to the „Deluxe“ version discernible when fitted include the following: On the -J255--A- fitted from the start of production onwards, the seat heating and seat ventilation are selected using the buttons -C- and the rotary pushbuttons. On the -J255--B- gradually introduced as of Model Year 2012, the seat heating and seat ventilation are actuated by way of 2 separate buttons -D- and -E-. In addition, the seat heating/seat ventilation on version -B- only has 3 settings (instead of 6 on version -A-). The seat heating setting selected is also reduced by one stage after a certain period of time (for more details, refer to → Owner's manual). Furthermore, the arrangement of certain buttons -F- and -G- is different on the two versions.
  A87-11096
t  On the „Basic“ model, the seat heating buttons are the only visible difference between the two versions -A- and -B- when fitted (on vehicles without seat heating, no particular differences between the versions are apparent when installed). On the -J255--A- fitted as of the start of production, the seat symbols in the buttons -C- and -D- face in different directions. On the -J255--B- fitted as of Model Year 2012, the seat symbols in the buttons -C- and -D- face in the same direction. On a -J255- of type -B-, the seat heating actuation only has 3 settings (instead of 6 on version -A-). The seat heating setting selected is also reduced by one stage after a certain period of time (for more details, refer to → Owner's manual).
  A87-11095
t  When the seat heating is switched on in the case of a -J255- fitted at the start of production for example, the function indicator lamp in button -A- or -B- lights („red“) and the seat heating setting selected appears for a certain period in the display of the air conditioner operating and display unit, Climatronic control unit -J255--C- and the MMI display. On the -J255- fitted as of Model Year 2012, the setting selected is displayed directly in the button by the lighting of indicator lamps. With these versions, the seat heating and seat ventilation can also be selected separately → Owner's manual, → Infotainment / MMI operating instructions. Attention is therefore to be paid to correct assignment of -J255- to the vehicle → Electronic parts catalogue.
t  The seat heating and ventilation settings are made on the air conditioner operating and display unit, Climatronic control unit -J255-. These settings are transmitted via the data bus to the onboard supply control unit -J519-. The specified temperatures for the various seat heating and ventilation settings are stored in the onboard supply control unit -J519-. Depending on the version of the onboard supply control unit -J519- and the vehicle production period, the specified temperature for the seat heating and seat ventilation may therefore differ in spite of identical settings on the air conditioner operating and display unit, Climatronic control unit -J255- → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (for the onboard supply control unit -J519-).
The following must additionally be heeded at present with regard to seat ventilation operation:
t  When the seat ventilation is switched on in the case of a -J255- fitted at the start of production, the function indicator lamp in button -B- lights („blue“) and the seat ventilation setting selected appears for a certain period in the display of the air conditioner operating and display unit, Climatronic control unit -J255--C- and the MMI display. On a -J255- gradually introduced as of Model Year 2012, the setting selected is displayed directly in the seat ventilation button by the lighting of indicator lamps → Owner's manual and → Infotainment / MMI operating instructions
t  The specified temperature for the seat is governed by the seat ventilation setting selected (approx. 33 °C in setting 1 and approx. 18 °C in setting 6). If the temperature measured in the seat is lower than the specified temperature, the seat heating is actuated until the specified temperature is attained → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (e. g. for the onboard supply control unit -J519-).
t  Seat heating may be switched in automatically by the control unit depending on the seat temperature and the seat ventilation setting selected. In seat ventilation mode, only the seat cushion is however heated if necessary, heating of the side bolsters is not activated → Current flow diagrams, Electrical fault finding and Fitting locations.
t  Actuation of the seat cushion and backrest fans (2 fans each in the backrest and seat cushion) is governed by the seat ventilation setting selected (approx. 40 % of maximum level in setting 1 and approx. 85 % in setting 6). At seat temperatures below 15 °C, the fans fitted in the seat are not actuated. The fans for the seat cushion and backrest are only actuated when a temperature of more than 15 °C is measured for this seat (the seat is heated by way of the seat heating element with seat ventilation switched on) → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (e.g. for the onboard supply control unit -J519-, -J136- and -J521-, depending on the vehicle) and → General body repairs, interior; Rep. gr.72 and → Rep. gr.74 (for component layout in the seat)
t  Actuation of the seat heating depends on the version of -J255- (3 or 6-stage seat heating or seat ventilation), the seat heating setting and the measured value of the temperature sensor in the seat cushion (actuation in setting 1 up to approx. 18 °C and in setting 3 / 6 up to approx. 40 / 60 °C) → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051. (e.g. for the onboard supply control unit -J519-, -J136- and -J521-, depending on the vehicle) and → General body repairs, interior; Rep. gr.72 and → Rep. gr.74 (for component layout in the seat).
t  In seat ventilation mode, additional heating is provided depending on the seat ventilation setting and the measured seat temperature (measured value of temperature sensor in seat cushion). It is also possible to reduce the output of the fans in the seat if the seat temperature is low → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (e. g. for the onboard supply control unit -J519-, -J136- and -J521- depending on the vehicle).
t  Seat ventilation is actuated by way of various control units depending on the vehicle model and equipment. The air conditioner operating and display unit, Climatronic control unit -J255- transmits information on the seat ventilation setting selected by way of the convenience data bus system to the corresponding control unit (depending on vehicle equipment and model to the seat and steering column adjustment control unit with memory -J136-, the front passenger seat adjustment with memory control unit -J521- and the onboard supply control unit -J519-) → Current flow diagrams, Electrical fault finding and Fitting locations. -J136- and -J521- then directly actuate the various fans fitted in the seats for example. By way of a LIN bus, the onboard supply control unit -J519- initially actuates the control unit for front right seat ventilation -J799- and if applicable the control unit for front left seat ventilation -J800- (depending on the vehicle equipment). -J799- and if applicable -J800- then actuate the various fans fitted in the seats for example → Current flow diagrams, Electrical fault finding and Fitting locations and → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (for -J519-, -J136- and -J521-).
  A87-10587

Checking air conditioner components on vehicles with a high-voltage system > < Checking of heated rear windowZ1