Chevrolet 2007 Express 2007 Express Owner's Manual page 135

Compass Calibration
The compass may need calibration if one of the
following occurs:
•
If CAL is displayed while driving in the vehicle.
•
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 in the compass/temperature button for
approximately nine 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 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, your
compass could give false readings.
To adjust for compass variance:
1. Find your current location and variance zone
number on the following zone map.
135