Compass Calibration; Compass Operation; Compass Variance - Cadillac SRX 2004 Owner's Manual

Compass Operation

Press the on/off button once to turn the compass
on or off.
When the ignition and the compass feature are on,
the compass will show two character boxes for
approximately two seconds. After two seconds, the
mirror will display the current compass heading.

Compass Calibration

If after two 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, note pad holder or similar object. If the letter C
should ever appear in the compass window, the compass
may need calibration.
The mirror can be calibrated by driving the vehicle in
circles at 5 mph (8 km/h) or less until the display reads a
direction.
The compass can be placed in calibration mode by
pressing and holding the on/off button until a C is shown
in the compass display.
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Compass Variance

Compass variance is the difference between earth's
magnetic north and true geographic north. If the mirror
is not adjusted for compass variance, your compass
could give false readings.
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 you live outside
zone eight. Under certain circumstances, such as a long
distance, cross-country trip, it will be necessary to
adjust the compass variance.