Automatic Dimming Mirror Operation; Compass Operation; Compass Variance; Compass Calibration - GMC 2008 Envoy Denali Owner's Manual

Automatic Dimming Mirror Operation

The automatic dimming mirror comes on each time the
ignition is turned to start. To turn the automatic dimming
feature off or back on, press the on/off button. The
indicator light on the mirror is lit when the automatic
dimming feature is on.

Compass Operation

Press the on/off button once to turn the compass
on or off.
There is a compass display in the window in the upper
right corner of the mirror face.

Compass Calibration

Press and hold the on/off button to activate the compass
calibration mode. CAL will be displayed in the compass
window on the mirror.
The compass can be calibrated by driving the vehicle
in circles at 5 mph (8 km/h) or less until the display
reads a direction.
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If after a few seconds the display does not show a
compass direction, (N for North for example), there may
be a strong magnetic field interfering with the compass.
Such interference may be caused by a magnetic antenna
mount, note pad holder, or similar object. If the letter C or
CAL appears in the compass window, the compass may
need to be reset or calibrated.

Compass Variance

Compass variance is the difference between earth's
magnetic north and true geographic north. The mirror
is set to 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, such as during a long distance
cross-country trip, it will be necessary to adjust for
compass variance. If not adjusted to account for compass
variance, your compass could give false readings.