GMC 2007 Envoy Denali Owner's Manual page 139

Automatic Dimming Mirror Operation
The automatic dimming mirror function is turned on
automatically each time the ignition is started.
To operate the automatic dimming mirror, do the
following:
1. Make sure the green indicator light, located to
the left of the on/off button, is lit. If it's not,
press and hold the on/off button until the green
light comes on, indicating that the mirror is
in automatic dimming mode.
2. Turn off the automatic dimming mirror function
by pressing and holding the on/off button until
the green indicator light turns off.
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. The compass
displays a maximum of two characters. For
example, "NE" is displayed for north-east.
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.
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.
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