Compass Calibration; Compass Variance - Chevrolet 2008 Silverado 1500 Pickup Owner's Manual

Compass Calibration

The compass may need calibration if one of the
following occurs:
•
After approximately five seconds, the display does
not show a compass heading, 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, magnetic
note pad holder, or a similar magnetic item.
•
The compass does not display the correct heading
and the compass zone variance is set correctly.
In order to calibrate, CAL must be displayed in the
mirror compass windows. If CAL is not displayed,
push the on/off button for approximately 12 seconds
or until CAL is displayed.
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

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.
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