Steering Wheel Heater (LRH), Function - GF46.11-P-0001LF

Model 217, 222 

with code 443 (Heated steering wheel) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON
• Interior temperature below 30°C

The electronic ignition lock control unit sends the status of circuit 15 to the steering wheel electronics over the suspension FlexRay, steering column tube module control unit and the steering LIN. The interior temperature value is sent by the climate control unit to the steering wheel electronics over the interior CAN, electronic ignition lock control unit, suspension FlexRay, steering column tube module control unit and the steering LIN.

Steering wheel heater, general 

It is possible to heat the steering wheel rim using the steering wheel heater.

The steering wheel heater function includes the following subfunctions:

• Switch steering wheel heater on/off 
• Automatic steering wheel heater switch off 

Switch steering wheel heater on/off 

The steering wheel heater is operated using the steering wheel heater switch in the steering column adjustment and steering wheel heater switch. The steering wheel heater is switched on or off by turning the steering wheel heater switch. The steering column tube module control unit reads in the status of the steering wheel heater switch directly.

On vehicles as from model year 2018, the steering wheel heater can also be operated using the voice control system (VCS). The head unit sends corresponding requests over the user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the steering column tube module control unit.

The steering column tube module control unit sends the status of the steering wheel heater switch or the request over the VCS over the steering LIN to the steering wheel electronics. Based on this, the steering wheel electronics activates or deactivates the steering wheel heater heating element in the steering wheel rim.

When the steering wheel heater is active, the steering wheel heater indicator lamp is actuated in the steering wheel heater switch. The surface temperature of the steering wheel rim is detected by the heating element temperature sensor. The steering wheel electronics reads in the signals of the heating element temperature sensor directly and regulates the surface temperature of the steering wheel rim to 35°C.

Automatic steering wheel heater switch off 

The timer control is implemented by the steering wheel electronics. After expiry of 15 min the steering wheel heater is automatically switched off.

The steering wheel heater timer control can be parameterized through the diagnosis tester.

Other shutoff criteria: 

• Shutoff in the event of a hardware defect: 
  • If actuation of the steering wheel heater is detected without an existing request or function requirement, the steering wheel electronics switch off the steering wheel heater and file a fault message in the fault memory.
• Switch off during overtemperature: 
  • If the vehicle interior temperature rises above 30°C, the steering wheel electronics switches off the steering wheel heater. The steering wheel heater indicator lamp remains on. If the vehicle interior temperature drops below the cutout temperature of 30°C, the steering wheel electronics automatically switch on the steering wheel heater again. The cutout temperature of the steering wheel heater can be parameterized through the diagnosis tester.

    The current interior temperature value is sent by the climate control, control unit to the steering wheel electronics via interior CAN, electronic ignition lock control unit, suspension FlexRay, steering column tube module control unit and steering LIN.

  If no plausible interior temperature value is present, the outside temperature value is used instead.

• Shutoff during engine starting procedure: 

  When the engine starts, the timer control runs on, and the steering wheel heater indicator lamp also remains on. An undervoltage is not defined during the starting procedure.

• Shutting off in the event of undervoltage: 

  At undervoltages of less than 10.0 V the steering wheel electronics switches off the steering wheel heater, and the steering wheel heater indicator lamp initially remains on. If the on-board electrical system voltage stabilizes within the next 3 min at normal voltage, the steering wheel heater automatically starts up again. If the shutoff last longer than 3 minutes however, then the steering wheel heater indicator lamp is also switched off. If the shutoff period persists and the function is requested again, the steering wheel heater indicator lamp lights up for 1.5 s and then goes out.

• Cutting out in the event of overvoltage: 

  At overvoltages greater than 15.5 V, the steering wheel electronics switches off the steering wheel heater. The timer control continues running, the steering wheel heater indicator lamp remains on. It can only be switched back on if the on-board electrical system voltage was stabilized at normal voltage. The overvoltage threshold of the steering wheel heater can be parameterized through the diagnosis tester.

• Shutoff after circuit 15R OFF: 

  If the terminal is changed from terminal 15R ON to terminal 15C ON, the timer control runs on for another 5 minutes. If terminal 15R is switched on again, the steering wheel electronics also switch the steering wheel heater back on.

• Shutoff at end of diagnosis: 

  After the diagnosis has completed, the steering wheel electronics switches off the steering wheel heater.

	Function schematic of electrical system for steering wheel heater		PE46.11-P-2050-97SEA
	Overview of system components of comfort heating systems		GF91.30-P-9990LF