GMC 1995 Jimmy Owner's Manual page 112

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. Locate your location on the zone map. Note your zone number.
2. Press and hold both the ON/OW and the US/MET switches. The
display will go off.
3. After 5 seconds, VAR CAL will appear on the display. When it does,
release both buttons.
4. Press US/MET until your zone number appears on the display.
5 . Press ON/OFF to enter your zone number. Your variance is now set.
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