Steering wheel heater (LRH), function - GF46.11-P-0001T
MODELS 211.0/2/6 up to 31.5.04 with CODE (443) Steering wheel heater
| 15.03.07 | The document has been updated to this date and will no longer be subject to revision. |
General information
In order to make hand contact more comfortable and safer at low temperatures, the steering wheel can be heated up via the steering wheel heater (LRH).
Operation takes place via the steering wheel heater switch (S59/1s2), control is taken over by the DC/DC converter control unit (N99).
The steering wheel heater (LRH) is operated with a voltage of 42 V or 48 V in order to produce the necessary output of 100 W. The voltage conversion is taken over by the DC/DC converter control unit (N99).
Function requirements
- Circuit 15R or circuit 15 ON
- Interior temperature < 30 °C
Switch on steering wheel heater (LRH)
- Rotate the steering wheel heater switch (S59/1s2) upwards.
- The signal is read in by the steering column module (N80) and transmitted via the CAN-B (CAN-B) to the DC/DC converter control unit (N99).
- 48 V is applied to the heater coil (R22/4r1) by the DC/DC converter control unit (N99) via the steering wheel heater electronics (A74). In order to protect it from overheating, it is switched over to 42 V after 7 minutes.
The temperate of the steering wheel rim is measured by the steering wheel heater electronics via the heater coil temperature sensor (R22/4b1) (A74) and used for the control.
The activated steering wheel heater (LRH) is displayed by the steering wheel heater function indicator (S59/1e1) in the steering wheel heater switch (S59/1s2).
Switching off steering wheel heater (LRH) manually
- Turn the steering wheel heater switch (S59/1s2) downwards.
- The signal is read in by the steering column module (N80) and transmitted to the DC/DC converter control unit (N99) via the CAN-B (CAN-B).
- The DC/DC converter control unit (N99) deactivates the steering wheel heater (LRH).
Switching off the steering wheel heater (LRH) automatically
- The maximum permanent heating time is 24 minutes. After this the heater coil (R22/4r1) is switched off by the DC/DC converter control unit (N99).
- At interior temperatures higher than 30 °C the steering wheel heater (LRH) is switched off in order to prevent overheating of the heater coil (R22/4r1). The interior temperature is transmitted by the overhead control panel control unit (N70) via CAN-B (CAN-B) to the DC/DC converter control unit (N99).
When the steering wheel heater (LRH) is deactivated the steering wheel heater function indicator (S59/1e1) in the steering wheel heater switch (S59/1s2) goes out.
Diagnosis
Diagnosis for the steering wheel heater (LRH) takes place through the request "read out fault" in the DC/DC converter control unit (N99).
Reading in the steering wheel heater switch (S59/1s2):
The position of the steering wheel heater switch (S59/1s2) is read out by the steering column module (N80) and placed on CAN-B (CAN-B). As long as the steering wheel heater switch (S59/1s2) is operated (turning up or down), the corresponding position is transmitted cyclically. The center position of the steering wheel heater switch (S59/1s2) is not transmitted by the steering column module (N80).
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