Cadillac 2008 DTS - Manual (Page 113)

Compass Variance
The zone is set to 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, 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 do the following:
1. Find the current location and variance zone number
on the following zone map.
2. Press and hold the on/off button until a zone
number appears in the display.
3. Once the zone number appears in the display,
press the on/off button quickly until the correct
zone number appears in the display. Stop pressing
the button and the mirror will return to normal
operation. If C appears in the compass window,
the compass may need calibration. See Compass
Calibration listed previously.
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