2006 Buick Lucerne Owner's Manual - Page 111

Compass Variance Compass variance is the difference between earth's magnetic north and true geographic north. 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. If not adjusted to account for compass variance, the 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 COMPASS button (or the on/off button for mirrors equipped with OnStar® controls) until a zone number appears in the display. 3. Once a zone number appears in the display, press the COMPASS button (or the on/off button for mirrors equipped with OnStar® controls) quickly until the correct zone number appears in the display. If C appears in the compass window, the compass may need calibration. See "Compass Calibration" explained previously. 2-35