2005 Chevrolet Astro Owner's Manual - Page 154

Compass Variance Variance is the difference between magnetic north and geographic north. In some areas, the difference between the two can be great enough to cause false compass readings. If this happens, follow these instructions to set the variance for your particular location: 1. Find your location on the zone map. Record your zone number. 2. Press and hold both the US/MET and the MODE buttons while in the COMP/TEMP mode. 3. After five seconds, the compass will acknowledge the variation mode by displaying the current zone number. When it does, release both buttons. 4. Press US/MET until your zone number appears on the display. 5. Press MODE to enter your zone number. Your variance is now set and the display will return to the COMP/TEMP mode. Setting the Variance Automatic Compass Calibration The compass is self-calibrating, so it does not need to be manually set. However, if C (Calibration) is displayed, the compass will need to be calibrated. You may also place the compass in a noncalibrated mode by pressing and holding the US/MET and MODE buttons simultaneously while in the COMP/TEMP mode. After about 10 seconds, the compass will display C and you can release the buttons. Drive the vehicle in a complete 360° circle three times at a speed of less than 5 mph (8 km/h), and the compass will function normally. Once the calibration is complete, the display will return to a compass reading. 3-38