The seat heating system heats the seat cushion area and backrest.
Seat heating can be switched on in two heating stages as from terminal 15 by pressing the button. Both LEDs built into the switch light to indicate operation.
Initially, heating stage 1 is activated when the seat heating is switched on (button pressed once). The seat surface is heated up to approx. 40 °C.
By pressing the button once more, the right LED goes out and heating stage 2 is activated. The seat is now only heated up to 37 °C.
The seat heating is switched off by pressing the button once again or switching off the ignition.
The seats are heated by means of carbon fibre heating mats. A carbon fibre heating mat is installed in both the seat cushion section as well as in the backrest. On sports seats, an additional, third carbon fibre mat is built into the thigh support. Only centre section of the seat cushion and backrest are heated. The side bolsters of the seat cushion and backrest are not heated.
The temperature is measured by a temperature sensor in the seat upholstery and passed on to the electronics integrated in the switch.
The electronic circuitry integrated in the switch controls and monitors the seat heating function.
Note
The electronic seat heating control switches off the power supply to the heating mats if the battery voltage in the vehicle is less than 11.4 V ±0.3 V. The function LED installed in the switch however remains on. Power supply to the heating mats is restored when the battery voltage is greater than 12.2 V ±0.3 V for at least 5 seconds.
The electronic seat heating control system monitors the temperature sensor and heating mats for faults.
If a break or short occurs at the temperature sensor, the seat heating is switched off in order to prevent overheating. The two function LEDs come on only briefly.
A flash code shows what faults the electronic circuitry has currently detected.
Flash code output is started by following procedure:
Initially, the seat heating is activated after pressing the button. Both LEDs come on. The right LED goes out after 10 seconds have elapsed. The flash code is output by the left LED. No fault was found if the right LED does not flash.
The following faults can be indicated by the left LED.
Flashing |
Defect |
|---|---|
Once |
Switch faulty (potentiometer or electronics) or switch overheating due to a short-circuit |
Twice |
Temperature sensor has break or short |
3 times |
Heating mat has break or short-circuit (probably break or short-circuit in wiring harness) |
The flash code can be repeated by briefly pressing the button twice.
Normal operation of the seat heating system can only be resumed after switching off the ignition.