Chevrolet 2007 Avalanche Owner's Manual page 147

Compass Variance
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 the vehicle is outside of zone eight. Under
certain circumstances, as during a long distance
cross-country trip, it will be necessary to adjust
for 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 compass
could give false readings.
To adjust for compass variance, do the following:
1. Find your current location and variance
zone number on the following zone map.
2. Press and hold the on/off button until a Z and
a zone number appears in the display. The
compass is now in zone mode.
3. Keep pressing the on/off button until the desired
zone number appears in the display. Release
the button. After approximately four seconds
of inactivity, the new zone number will be
locked in and the compass/temperature
display will return.
4. Calibrate the compass as described next.
I n f o r ma t i o n P r o v i d e d b y :
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