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Calibrate Your Compass

This tech article was originally posted at FordF150.net. It is intended for any Ford vehicle that has the compass display in the inside rearview mirror.

Because the vehicle's sheet metal magnetism tends to change over time, the compass may lose accuracy and need to be calibrated. This condition is indicated if the True North Adjustment does not correct an inaccurate compass. A compass that is newly installed in a vehicle must also be calibrated. The compass is calibrated as follows:

  1. Find an open area free from steel structures and high voltage power lines
  2. Ensure that all doors are closed and the map lamp in overhead console is off
  3. Place a paperclip, toothpick, or similar object into the compass recessed button "A" hole (by temperature button) and push up gently until the CAL indicator turns ON. Release recessed button.
  4. Slowly drive vehicle less than 5 km/h (3 mph) in a circle until the CAL indicator turns OFF. At this point, calibration is complete.
  5. Perform Compass True North Adjustment as outlined.

NOTE: The electronic compass senses magnetic North to determine direction. Most roads and maps are based on geographic "true north", which varies considerably from magnetic north across the country. Components made of ferrous metals (such as iron and steel) and vehicle electrical accessories affect compass readings, by changing the magnetic field.

Compass True North Adjustment

Compass/thermometer calibration and vehicle demagnetizing have been performed by the manufacturer. However, the True North Adjustment has not been performed. Vehicle location will determine how accurate the compass is without performing the True North Adjustment.

In coastal or mountainous areas the differences between true north and magnetic north vary considerably. Whenever a vehicle is received from the manufacturer or whenever a compass is thought to be inaccurate, the first step taken should be to perform the True North Adjustment. The compass True North Adjustment is set as follows:

  1. Place a paperclip, toothpick, or similar object into compass recessed button "B". Push up gently and hold until the word VAR lights up and a number 1 appears to the left of VAR. Remove object from adjustment hole
  2. Determine which zone of the country you are in by use of the map below
  3. Press compass button until the correct zone number appears
  4. Complete the true north setting by again placing a paperclip or a similar object in the compass recessed button "B" and push up gently and release

Compass Calibration Diagram
(sorry for the poor quality)

This article has been republished with permission from LincolnsOnline.com.