Hummer 2008 H2 - Manual (Page 129)

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 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. Compass variance is
the difference between earth’s magnetic north and true
geographic north. If not adjusted to account for
compass variance, your compass could give false
readings.
To adjust for compass variance:
1. Find your current location and variance zone
number on the following zone map.
2. Press and hold the compass/temperature button for
five seconds until a zone number appears in the
display.
Cleaning the Mirror
When cleaning the mirror, use a paper towel or similar
material dampened with glass cleaner. Do not spray
glass cleaner directly on the mirror as that may cause
the liquid cleaner to enter the mirror housing.
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