1999 Buick Riviera Owner's Manual - Page 111

yellowblue To adjust for compass variance: 1. Press and hold the COMPASS button located at the bottom of the mirror until a zone number appears in the display. 2. Find your current location and variance zone number on the following zone map. 3. Press the COMPASS button on the bottom of the mirror until the new zone number appears in the display. After you stop pressing the button, the display will show a compass direction within a few seconds. (This is the automatic calibration mode. Drive in a circle to calibrate the mirror. See "Compass Calibration" explained previously.) 2-49