Steering wheel heater (LRH), function - GF46.11-P-0001M: Notes

MODEL 220.025 /026 /028 /063 /065 /067 /070 /073 /074 /075 /083 /084 /087 /125 /126 /128 /165 /167 /170 /173 /174 /175 /176 /178 /183 /184 /187 /874 /875 /876 /878 with CODE (443) Steering wheel heater

MODEL 215.373 /374 /375 /376 /378 with CODE (443) Steering wheel heater

Shown on Model 220

Fig 1: Identifying Steering Column Module, EIS Control Module - Shown On Model 220

Operation

Using the steering wheel heater the steering wheel can be heated up to make finger contact more comfortable and safer at low outside temperatures.

The steering wheel heater is switched on and off by a rotary function of the steering wheel heater switch. The position of the steering wheel heater switch is read out by the electronics in the steering column module (N80) and placed on CAN class B.

There are 3 positions for the steering wheel heater switch:

Center position
Turning upwards
Turning downwards

A red function LED to display function is integrated in the steering wheel heater switch. The function display is switched off in the event of a defect in the steering wheel heater.

The DC/DC converter control module (N99) directs voltage to the steering wheel heater electronics fitted in the steering wheel. This energizes the heating coils in the steering wheel in order to heat up the steering wheel and regulates the steering wheel heater to the target temperature of approx. 28 °C at the steering wheel surface.

The information as to whether heating or an internal diagnosis (steering wheel self check) should be carried out is conveyed to the steering wheel heater electronics by means of a different voltage level at its inlet.

Tasks of steering wheel heater electronics:

To energize the heating coil in the steering wheel
To measure the surface temperature of the steering wheel rim via the integrated temperature sensor
To carry out diagnosis for the heating coil and temperature sensor in the steering wheel rim

Two power settings are possible:

To heat with minimum power (voltage supply 42 V)
To heat with maximum power (voltage supply 48 V)

It is necessary to increase the voltage from 12 V to 42 V or 48 V so that the steering wheel heater can be supplied with a power of approx. 100 W.

To enable rapid heating up the heating coil is supplied with 48 V when it is switched on.

The time is limited to 7 minutes to prevent it from overheating. After this the heating coil is supplied with minimum power (voltage supply 42 V).

The maximum permanent heating time is 24 minutes. The heating coil is switched off after this.

The system is controlled and monitored by the DC/DC converter control module (N99).

The interior temperature is reported to the DC/DC converter control module (N99) by the overhead control panel control module (N70) via the CAN class B. The DC/DC converter control module (N99) evaluates the interior temperature signal to protect the heating coil.

	Steering wheel heater (LRH), networking of components		GF46.11-P-0001-01M
	Switching steering wheel heater (LRH) on/off, function		GF46.11-P-1001M