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

MODEL 166 as of model year 2016 with CODE 443 (Steering wheel heater) 

MODEL 292 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 via chassis CAN 1, the steering column tube module control unit and steering LIN to the steering wheel electronics.

The automatic air conditioning control and operating unit transmits the interior temperature value via interior CAN, the electronic ignition lock control unit, chassis CAN 1, the steering column tube module control unit and the steering LIN to the steering wheel electronics.

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:

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

Manual on/off function sequence 

It is operated using the steering wheel heater switch, which is integrated into the steering column adjustment switch and steering wheel heater.

The steering wheel heater is switched on or off by turning the steering wheel heater switch. 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 continuously checks the function of all involved components of the steering wheel heater and sends the corresponding status via steering LIN to the steering column tube module control unit. When the steering wheel heater is switched on, 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 

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.

Other shutoff criteria:

• 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 the cutout temperature T = 30 °C, the steering wheel heater is switched on again automatically.

  The automatic air conditioning control and operating unit transmits the current interior temperature via the interior CAN, the electronic ignition lock control unit, chassis CAN 1, the steering column tube module control unit and the steering LIN to the steering wheel electronics.

  The cutout temperature of the steering wheel heater can be parameterized through the diagnosis tester.

  Shutoff in the event of an error (short circuit, overload or open circuit (line break)):

  The steering wheel electronics detects a possible short circuit, overload or a line break in the respective steering wheel heater heating element and deactivates the power supply. The fault sources that have been listed can be diagnosed individually using a diagnostic tester.

• Shutoff when the engine starts:

  When the engine is started (cold start), the steering wheel heater is deactivated for t = 20 s. During a hot start, the steering wheel heater is deactivated for t = 3 to 5 s. Timer control continues running and the steering wheel heater indicator lamp remains switched on. No undervoltage is detected during startup.

• Switching off by energy management:

In order to prevent the battery from discharging in all driving cycle phases, the state of charge is continuously evaluated. Depending on the situation, the steering wheel heater is also deactivated if necessary.

If the steering wheel heater is switched off, the steering wheel heater indicator lamp initially remains switched on. If the on-board electrical system reaches its on-board electrical system voltage again within the next t = 3 min, the steering wheel heater function also starts 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 via the steering wheel heater switch, the steering wheel heater indicator lamp lights up for t = 1.5 s and then goes out again.

• Shutoff in the event of voltage loss:

  If one of the two respective supply lines (circuit 30 or circuit 30g) of the steering wheel electronics fails, the steering wheel heater is switched off.

• Shutoff after circuit 15R OFF:

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

• Shutoff in the event of "Timeout error":

  If the request of the steering column tube module control unit for actuating the steering wheel heater is discontinued or a "Timeout period" from the electronic ignition lock control unit is recognized, the steering wheel heater is switched off.

• 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-2050-97NBA
	Overview of system components of comfort heating systems		GF91.30-P-9990GN