Ford F-650 2001 Owner's Manual page 72

Controls and features
The compass reading may be affected when you drive near large
buildings, bridges, power lines and powerful broadcast antenna. Magnetic
or metallic objects placed in or on the vehicle may also affect compass
accuracy. Adjustments may need to be made to the zone and calibration
of the compass.
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.
1
2. Locate the controls on the
15
overhead console.
2
14
3. Turn ignition to the ON position.
3
13
4
12
11
5
6
10
8 9
7
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