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

MODEL 166 up to model year 2016 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 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.

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 

The steering wheel heater switch integrated into the steering column adjustment and the steering wheel heater switch are used for operation. The steering wheel heater is switched on or off by turning the steering wheel heater switch.

The request from the steering wheel heater switch is read in by the steering column tube module control unit and sent via the steering LIN to the steering wheel electronics. Based on this, the steering wheel electronics activates the steering wheel heater heating element in the steering wheel rim. The steering wheel heater indicator lamp in the steering wheel heater switch is actuated at the same time.

The heating element temperature sensor measures the surface temperature of the steering wheel rim and transmits the value to the steering wheel electronics.

The steering wheel electronics regulate the surface temperature of the steering wheel rim to T = 35 °C.

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.

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.

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 cut-in temperature 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.

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 is detected during startup.

• Shutting off in the event of undervoltage:

In the event of undervoltage U < 10.0V, the steering wheel electronics switches off the steering wheel heater; the steering wheel heater indicator lamp remains on initially. 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:

In the event of overvoltage U > 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.

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 diagnosis has finished, the steering wheel heater is switched off.

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