Calibrating the Compass, Function

NOTE:
If the voltage supply is Interrupted, e.g. if the battery is disconnected or flat, the electronic compass (B26) must be recalibrated.
During this process the electronic compass (B26) measures the magnetic conditions around the vehicle. The compass thus compensates for magnetic interference which would otherwise cause incorrect routes to be displayed.


Calibrating the compass
Requirements:
The compass must be calibrated in an open space. To avoid magnetic Interference, do not attempt to calibrate the compass near to steel constructions, power lines, radio masts or the like. Furthermore, ensure that all electric consumers, in particular those with a high power input, are switched off.
Close all doors inducing the tailgate. (The message "DOOR OPEN" appears on the display of the trip computer control module (N41) if the tailgate is open.)

Start engine
Press the Mode button (right button, N41s2) until the compass appears on the display of the trip computer. Press the Reset button (left button, N41s1) once Press the Mode button (right button, N41s2) once. The word "CAL" now appears on the display (calibration mode) Calibration drive: Drive the vehicle in a complete circle at a speed of less than 5 km/h.
Once the compass has been calibrated successfully, the trip computer display jumps automatically to the compass display.
If the display does not return to the compass display, repeat the calibration drive.


NOTE: Calibration drive
During the calibration drive, it is important that the compass runs through all directions. The quickest way to complete the compass calibration is therefore to drive the vehicle on a circular course; the tangent of a circle points in a different direction at each point of the drive.
It is also possible to calibrate the compass by driving the vehicle on a "normal" route, but then the calibration time depends on the route and the speed at which the vehicle is driven.


NOTE: Automatic calibration
If the compass detects strong magnetic fluctuations In its vicinity, the compass changes automatically to the calibration mode. The word "CAL" appears in the display of the trip computer. The compass is then calibrated as described above by performing a calibration drive.


NOTE: Magnetic surroundings
Ferromagnetic materials (e.g. iron and nickel) influence the magnetic field around them and therefore also the local magnetic field of the earth used to calibrate the compass.
The same applies for electric currents. Every current-carrying conductor is surrounded by a magnetic field. The strength of this magnetic field depends on the intensity of the current. For this reason, the requirements mentioned above must be observed when calibrating the electronic compass.


NOTE: Influence of the tailgate on the compass
The electronic compass (B26) is located below the tailgate. The magnetic field around the compass differs greatly, therefore, depending on whether the tailgate is open or closed. When the tailgate is open, the route is therefore not displayed on the trip computer (N41) and "--"appears on the display. The signal of the tailgate rotary tumbler microswitch (S88/11) is used here. The signal is read in by the all activity module (AAM, N10) (also for central locking) and passed as a CAN message to the trip computer control module (N41).