Saturn 2005 Ion Owner's Manual page 101

Compass Variance
Compass variance is the difference between earth's
magnetic north and true geographic north. If not
adjusted to account for compass variance, the mirror's
compass could give false readings. The mirror is
set in zone eight upon leaving the factory. It will be
necessary to adjust the compass to compensate
for compass variance if you live outside zone eight.
Under certain circumstances, as during a long distance
cross-country trip, it will be necessary to adjust for
compass variance.
To adjust for compass variance:
1. Find the current location and variance zone number
on the following zone map.
2. Press and hold the on/off button for five seconds
until the word ZONE appears in the display. The
compass is now in zone mode.
3. Press and release the on/off button within five
seconds until the new zone number appears in
the display. The display will show a compass
direction within a few seconds.
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