2004 Chevrolet Colorado Owner's Manual - Page 122

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. To adjust for compass variance, do the following: 1. Find your current location and variance zone number on the zone map that follows. 2. Press and hold the on/off button until a zone number appears on the display. 3. Once the zone number appears on the display, press the on/off button quickly until you reach the correct zone number. 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. 2-40