FORD 1998 Expedition - Manual (Page 43)

Usually, when something affects
the compass readings, the compass
will correct itself after a few days
of operating your vehicle in normal
conditions. If the compass still
appears to be inaccurate, a manual
calibration may be necessary. Refer
to Compass calibration
adjustment.
Most geographic areas (zones)
have a magnetic north compass
point that varies slightly from the
northerly direction on maps. This
variation is four degrees between
adjacent zones and will become
noticeable as the vehicle crosses
multiple zones. A correct zone
setting will eliminate this error.
Refer to Compass zone
adjustment.
Compass zone adjustment
1. Determine which magnetic zone
you are in for your geographic
location by referring to the zone
map.
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Controls and features
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