Correction of signals from electronic compass, function

The current flowing through the rear window defroster (R1) generates a magnetic field when it is switched on. This is superimposed on the earth magnetic field interrupting the function of the electronic compass (B26). This can lead to erroneous navigation by the auto-pilot system (APS). To avoid navigation errors the current is measured so that the interrupting magnetic field can be taken into consideration in evaluating the value from the compass signal.

Function
The power for the rear window defroster (R1) flows through the rear window defroster measuring resistor (R1/2).
The voltage drop across R1/2 is measured by the APS navigation

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processor (A2/30) for correction of the direction values from the electronic compass (B26) when the rear window defroster is switched on.

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Location of measuring resistor:

Model 210 up to 31.05.96

R1/2 is located below the rear shelf.

Model 210 as of 01.06.96

R1/2 is mounted between the rear seat backrest and trunk divider panel.

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