Compass calibration, function - GF54.50-P-2013GH

MODEL 163 as of 1.9.00 with CODE (245) Trip computer 

If the voltage supply is interrupted  , e.g. if the battery is disconnected or flat, the electronic compass (B26)  must be re-calibrated. In this process the electronic compass (B26)  measures the magnetic fields around the vehicle. In this way the compass is able to compensate for magnetic interference which could otherwise result in course errors.

Automatic calibration 

If the compass detects strong magnetic fluctuations in its vicinity, the compass changes automatically  to the calibration mode. The word "CAL"  appears on the trip computer display. The compass is then calibrated as described below by means of a calibration drive  .

Calibration drive 

During the calibration drive it is important that the compass runs through all the points of the compass. The calibration sequence is therefore completed more quickly if the calibration drive is performed on a circular circuit; the tangent on a circle has a different orientation at each point on the circle. The compass can also be calibrated by "normal" driving, although the time required for calibration is then heavily dependent on the route and the speed at which the vehicle is driven.

Influence of the tailgate on the compass 

Because the electronic compass (B26)  is located below the tailgate, the magnetic field around the compass varies considerably depending on whether the tailgate is open or closed.

For this reason if the tailgate is open, the course disappears from the trip computer (N41)  and the display shows "-"  .

For this the system uses the signal from the tailgate rotary tumbler microswitch (S88/1)  . The signal is read in by the all-activity module (AAM, N10)  (also for central locking) and relayed in the form of a CAN message to the trip computer control module (N41)  .

Magnetic environment 

Ferrous materials (e.g. iron and nickel) influence the magnetic environment around them and therefore also have a localized effect on the earth's magnetic field, which the compass uses for calibration.

The same applies for electrical 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 these reasons, the requirements mentioned above must be observed when calibrating the electronic compass.

Calibrating the compass 

• Requirements: 

  The compass must be calibrated in open country  .

  To avoid magnetic interference, this must not be done in the vicinity of steel structures, power lines or radio transmitters. Furthermore, ensure that all electric consumers, in particular those with a high power input, are switched off.

• Close all doors including the trunk lid or tailgate. (If the tailgate is open, the display of the trip computer control module (N41)  shows the message "DOOR OPEN").

  Calibration up to 31.08.01 

• 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  " (calibration mode) appears on the display.

  Calibration drive 

  Drive the vehicle in a full circle  at a speed below 5 km/h  .

• Once the compass has been calibrated successfully, the trip computer display jumps automatically  to the compass display.
• If the display fails to return to the compass, the calibration drive must be repeated.

Calibration as of 01.09.01 

• 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. The compass chart is displayed.
• Press the Mode button (right button, N41s2)  , repeatedly.
• Hold a the Reset button (left button, N41s1)  for longer then 2 seconds. To confirm entry into calibration mode. The word "CAL"  appears on the display.

  Calibration drive 

• Drive two circles  in open country  at a speed below 5 km/h  . Read the notes under the heading "Magnetic environment  "
• Rear window defroster switched off.
• Stop the vehicle and wait 5 seconds  .
• Switch the rear window defroster on  and wait 5 seconds  with the vehicle stationary.
• The display should now change back to the compass display automatically. If not, the calibration drive must be repeated.
• Switch off rear window defroster.
• Calibration drive complete.

Trip computer control module, location / task / design	GF54.50-P-4100GH
Electronic compass, location / task / design	GF54.50-P-4101GH