Seat Temperature Element: Testing and Inspection

Heated Seats, Checking

• If there is a condition that prevents the driver or passenger seat heating from switching on such as a short circuit in the connection to the seat heating element or an open circuit in the voltage supply to the Climatronic Control Module (J255) front A/C control head, this will be stored as a fault in the control head vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.

• The function test for the heated seat activation is described in A/C system Guided Fault Finding Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function

• If the voltage measured at the Energy Management Control Module (J644) at terminal "30" falls below a value stored in the control module, the seat heater output to reduced to approximately 50% or switched off completely to relieve the load on the alternator the Climatronic control Module (J255) front A/C control head Rear A/C Control Head (Climatronic) (E265) reduces the activation duty cycle from 100% to between 905 and 0%) Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

• The measured value block for the Climatronic Control Module (J255) front A/C control head indicates if the front seat heater is switched on or why there no activation even though there is a request Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

• The Rear A/C Control Head (Climatronic) (E265) measured value block indicates if the rear seat heater is switched on or why there is no activation even though there is a request. Front Climatronic Control Module (J255) indicates that rear seat heater has been switched off due to excessive load on vehicle electrical system Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

• On vehicles without a Rear A/C Control Head (Climatronic) (E265), rear seat heater activation is not shown in OBD. Check the activation wiring diagrams, Troubleshooting & Component locations and Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

Specified temperatures for seat heater are different on vehicles with or without seat ventilation values indicated in the following table are approximate values, exact value depends on control module version. The permitted tolerance range is currently * / - 4 °C (* / - 6 °C for level "6" on vehicles with seat ventilation) because regulation corresponds to a characteristic curve so the specified temperature of the next higher level is always greater than the lower level Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.