Chevrolet 2013 Express Owner's Manual page 109

Compass variance is the difference
between the earth's magnetic north
and true geographic north. If the
compass is not set to the zone
where you live, the compass may
give false readings. The compass
must be set to the variance zone in
which the vehicle is traveling.
To adjust for compass variance, use
the following procedure:
Compass Variance (Zone)
Procedure
1. Do not set the compass zone
when the vehicle is moving. Only
set it when the vehicle is in
P (Park).
Press until PRESS
CHANGE COMPASS ZONE
displays.
2. Find the vehicle's current
location and variance zone
number on the map.
Zones 1 through 15 are
available.
TO
3. Press to scroll through and
select the appropriate
variance zone.
4. Press
heading, for example, N for
North, is displayed in the DIC.
Instruments and Controls
until the vehicle
5. If calibration is necessary,
calibrate the compass. See
Compass Calibration
Procedure following.
Compass Calibration
The compass can be manually
calibrated. Only calibrate the
compass in a magnetically clean
and safe location, such as an open
parking lot, where driving the
vehicle in circles is not a danger.
It is suggested to calibrate away
from tall buildings, utility wires,
manhole covers, or other industrial
structures, if possible.
If CAL should ever appear in the
DIC display, the compass should be
calibrated.
If the DIC display does not show
a heading, for example, N for
North, or the heading does not
change after making turns, there
may be a strong magnetic field
interfering with the compass.
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