Steering wheel heater (LRH), function - GF46.11-P-0001RF

MODEL 205, 253 with CODE 443 (Steering wheel heater) 

Function requirements, general 

• Circuit 15R ON
• Interior temperature T < 30 °C

The electronic ignition lock control unit sends the status of circuit 15 to the steering wheel electronics over the chassis 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, chassis 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.

MODEL 205 (except 205.012/047/147/212/247)

with CODE 443 (Steering wheel heater)

with CODE 577 (Remote activation of heating and ventilation systems)

MODEL 205.012/047/147/212/247

with CODE 443 (Steering wheel heater)

The pre-entry climate control function activates the steering wheel heater for a maximum of t = 60 s after unlocking of the vehicle. The steering wheel is thereby heated prior to driving off.

The steering wheel heater function includes the following subfunctions:

• Manual on/off function sequence 
• Function sequence for automatic switch off 

Manual on/off function sequence 

Turning the steering wheel heater switch on the steering column adjustment and the steering wheel heater switch switches the steering wheel heater on or off.

The signals from the steering wheel heater switch are read in by the steering column tube module control unit and sent to the steering wheel electronics via steering LIN. Based on this, the steering wheel electronics activates or deactivates the steering wheel heater heating element in the steering wheel rim.

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 T = 35 °C.

The steering wheel electronics sends the status of the steering wheel heater to the steering column tube module control unit. When the steering wheel heater is activated, the steering wheel heater indicator lamp in the steering wheel heater switch is actuated by the steering column tube module control unit.

Function sequence for automatic switch off 

If one of the following criteria occurs, the steering wheel heater is switched off automatically:

• Switchoff by timer control: 

  The timer control is implemented by the steering wheel electronics. After expiry of t = 15 min the steering wheel heater is switched off automatically. The steering wheel heater timer control can be parameterized through the diagnosis tester.

• Shutoff in the event of a hardware defect: 

  If an actuation of the steering wheel heater is detected without an existing request or function requirement, then the steering wheel heater is switched off and a fault message is stored in the fault memory.

• Switch off during overtemperature 

  If the interior temperature rises above T = 30 °C, the steering wheel electronics switch off the steering wheel heater. The steering wheel heater indicator lamp remains on. If the interior temperature drops below T = 30 °C, the steering wheel heater is automatically switched on 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 unit to the steering wheel electronics via interior CAN, electronic ignition lock control unit, chassis 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: 

  The timer control continues running, the steering wheel heater indicator lamp also remains on. No undervoltage assessment takes place during startup.

• Shutting off in the event of undervoltage: 

  At a voltage of U < 10.0 V, the steering wheel electronics switches the steering wheel heater off. The steering wheel heater indicator lamp remains on at first. If the on-board electrical system reaches is its normal voltage again within the following time of t = 3 min, the steering wheel heater starts again automatically. If the shutoff takes longer than t = 3 min, the steering wheel heater indicator lamp is also switched off. If the shutoff continues and the function is requested again, the steering wheel heater indicator lamp lights up for t = 1.5 s and then goes out again.

• Cutting out in the event of overvoltage: 

  At a voltage of U > 15.5 V, the steering wheel electronics switches the steering wheel heater off. The timer control continues running, the steering wheel heater indicator lamp remains on. Switching on again is only possible after a permissible voltage is applied again. The overvoltage threshold of the steering wheel heater can be parameterized through the diagnosis tester.

• Shutoff after circuit 15R OFF: 

  If circuit 15C remains ON, the timer control runs on for t = 5 min. If circuit 15R is now switched on again, the steering wheel heater is also switched on.

• Shutoff at end of diagnosis: 

  After the diagnosis has finished the steering wheel heater switches off.

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