Seat Heater Activation
Seat Heater Activation
=> [ With Automatically Regulated A/C System ]
=> [ With Manually Regulated A/C System ]
• From MY 2009, as a running change, the Climatronic Control Module (J255) (or control modules for seat heating) is being installed, whereby the specified temperature is set to a lower characteristic line. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
With Automatically Regulated A/C System
Climatronic Control Module (J255) activation
• 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 the "Guided Fault Finding" function.
• The function test for the heated seat activation is described in A/C system Guided Fault Finding using vehicle diagnosis, testing and information system VAS 5051.
• From MY 2010, this vehicle has a Start/Stop System for specific engines as optional equipment. On vehicles with the Start/Stop System, seat heating and ventilation is switched off whenever the Stop function is active (by the Vehicle Electrical System Control Module (J519) to protect the battery). After the engine is started again by the Start function, seat heating and ventilation is switched on again. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
• If the voltage measured on terminal 30 falls below the value stored in the vehicle electrical system control module, then the heat seating power will be switched off completely to take the load off the generator. The Climatronic control module electronics reduces the duty cycle from 100% to less than 90 to 0.0%. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
• Climatronic control module measured value block indicates the front seat heater is switched on or why no activation is occurring despite a request. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
With Manually Regulated A/C System
A/C Control Module (J301) activation
• On vehicles with manual climate control system, activation of heated seats is not monitored by the A/C Control Module (J301) electronics, therefore malfunctions are not stored in DTC memory.
• The A/C control module provides a voltage via the Heated Driver Seat Adjuster (E94) and Heated Front Passenger Seat Adjuster (E95) (a potentiometer is operated via the respective knurled wheel - C -).
• The voltage supplied by A/C control module - A - with seat heater switched on is dependent on the knurled wheel position and on the vehicle voltage supply, it is in the range of less than 0.5 volts in position 0 to approximately 10 volts in position 5 (measured to Ground -GND- e.g. at connector - B - terminal 20) with engine running. The voltage is transferred via connector - B - (from terminal 13 to Driver Seat Heater Control Module (J726) and from terminal 12 to Front Passenger Seat Heater Control Module (J727)).
• Resistance of seat heater potentiometer is dependent on the knurled wheel position, it cannot be measured using workshop equipment.
• Check function of seat heater and service it.