Rear Window "Defroster ON" Signal (Mark I Only)
On Mark I navigation systems, the magnetic field sensor (compass) can be falsely influenced by magnetic fields which are not from the earth's natural magnetic field. The magnetic field sensor is installed under the rear parcel shelf, which is in close proximity to the rear window defroster. This creates the need for a signal compensation when the rear defroster is switched on.
The compensation is derived from the dealership calibration procedures (see WORKSHOP HINTS ).
When the rear defroster is ON, the navigation computer receives the ON signal via the bus network. As the illustration shows, the signal is sent via the following pathway:
IHKA module > K-Bus > IKE > I-Bus > Video Module > ARCNET> Navigation