GMC 2006 Sierra - Manual (Page 159)

To adjust for compass variance, do the following:
1. Find your current location and variance zone
number on the map.
2. Press and hold the on/off button for six seconds.
Release the button when ZONE is displayed. The
number shown is the current zone number.
3. Scroll through the zone numbers that appear in
the compass/temperature window on the mirror by
pressing the on/off button. Once you find your zone
number, release the button. After about four
seconds, the mirror will return to the compass
display, and the new zone number will be set.
Automatic Dimming Rearview
Mirror with Compass and
Temperature Display
If the vehicle is equipped with an automatic mirror,
it will, when on, automatically dim to the proper level
to minimize glare from lights behind you after dark.
The mirror also includes a display in the upper right
corner of the mirror face. The compass reading and the
outside temperature will both appear in the display at the
same time. The dual display can be turned on or off by
briefly pressing either the TEMP or the COMP button.
Temperature Display
The temperature can be displayed by pressing the TEMP
button. Pressing the TEMP button once briefly, will toggle
the temperature reading on and off. To alternate the
temperature reading between Fahrenheit and Celsius,
press and hold the TEMP button for approximately
four seconds until the display blinks F and C. Press
and release the TEMP button to toggle between the
Fahrenheit and Celsius readings. After approximately
four seconds of inactivity, the display will stop blinking
and display the last selection made.
If an abnormal reading is displayed, for an extended
period of time, please consult your dealer. Under certain
circumstances, a delay in updating the temperature is
normal.
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