Heated Seats and Seat Ventilation, Checking
Heated Seats and Seat Ventilation, Checking
Heated Seats without Seat Ventilation, 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) , this will be stored as a fault in the Climatronic control module. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• The function test for the heated seat activation is described in A/C system Guided Fault Finding in the Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• If there is a condition at which heater of rear seats cannot be switched on (short circuit in connection to seat heating element, open circuit in voltage supply tour Rear A/C Display Control Head (E265) ), this is stored as a fault in the rear A/C display control head. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• If the voltage measured at the Energy Management Control Module (J644) at terminal 30 falls below a value stored in the energy management control module the seat heater output is reduced to approximately 50% or the seat heating is switched off completely to relieve the load on the generator (by the Climatronic control module electronics / rear A/C display control head reduces the activation duty cycle from 100% to 90 to 0%). Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• Measuring value block of Climatronic control module indicates that heater for front seats is switched on or why no activation is occurring despite a request. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• Measuring value block of rear A/C display control head indicates that heater for rear seats is switched on or why no activation is occurring despite a request. Climatronic control module indicates that rear seat heater has been switched off for example, due to excessive load on vehicle electrical system. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• On vehicles without a rear A/C display control head, rear seat heater activation is not shown in OBD. Check the activation using and Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• On vehicles with seat occupied recognition system, seat heaters can be switched off after approximately 10 minutes if it is recognized that this seat is not occupied (for example, check the Airbag Control Module (J234) measured values block) using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
The specified temperatures for the seat heating are different on vehicles through MY 09 and from MY 10. On vehicles from MY 10, the specified temperatures for seats with and without seat ventilation are currently the same (values indicated in the following table are approximate values, exact value depends on control module version) The permitted tolerance range is currently (* / - 4 °C * (24.8 °F) / - 6 °C (21 F) for level "6") because regulation corresponds to a characteristic curve so the specified temperature of the next higher level is always greater than the lower level. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
Heated Seats with Seat Ventilation, Checking
• The information is exchanged via the Data bus system (LIN bus) between the Climatronic control module and the control modules for the seat ventilation.
• Depending on the vehicle equipment level, it involves the following control modules ( Driver Seat Ventilation Control Module (J672) and Front Passenger Seat Ventilation Control Module (J673) ). Refer to and Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• The Climatronic control module sends the request to switch on the seat heating / seat ventilation vie the local data bus to the respective control unit (the control unit depends on the vehicle version and vehicle equipment level. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" for each control unit). (for the respective control module).
• Activation of information to these control modules is displayed in measured value block of the Climatronic control module, check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• Currently the rear seat do not have seat ventilation.
• The current front seat ventilation and heating level is displayed in the measured value blocks for the Climatronic control module using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• Seat ventilation is optional equipment. It was introduced as a running change as of MY 10. Make sure the vehicle has the correct version of the Climatronic control module. Refer to the Electronic Parts Catalog.
Checking the activation
• Perform a functionality test on the seat ventilation blower using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• The seat ventilation blower activation is not displayed directly. The blower activation can be checked via the seat ventilation control module as follows.
- Switch the electrical consumers with high current consumption off (for example, the rear window defroster).
- Select the lowest speed possible for the Fresh Air Blower (V2).
- Adjust the seat ventilation control (in the front or rear A/C control head) to the highest level.
- Check the seat to see if the sound of the fan running is audible.
- Set the seat heating control (in the front A/C control head) to the highest level. The measured value block shows that the seat heating is switched on, check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
• At this time, heed the following when operating seat ventilation:
- Seat ventilation is not available when the seat temperature is less then 15 °C (59 °F). It will switch off due to low seat temperature.
- Depending on seat temperature and selected level of seat ventilation, seat heater can be switched on automatically by control module after approximately 5 min. in seat ventilation mode. If necessary, only the seat cushion in heated. The side bolster heating is not switched on.
- Depending on the level selected, the seat ventilation may heat the seat to the following temperature (measured value for the temperature sensor in the seat surface), check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".
