1998 GMC Suburban Owner's Manual - Page 126

The normal display will show a temperature reading in degrees Fahrenheit or Celsius. If an abnormal reading is displayed, please consult your dealer. Compass Calibration Electrochromatic Mirror Operation The right side of the switch, labeled TEMP, located at the bottom of the mirror turns the electrochromic inside and outside mirrors on and off. An indicator light, located to the right of the TEMP switch, will come on when the electrochromic mirrors are turned on. To turn the mirrors on, press and hold the TEMP button for six seconds. Themirrors will darken and remain dark until the button is released. To turn the mirrors off, press and hold the TEMP button for six seconds. If, after two seconds, the display does not show a cornpass heading ("N" for North, for example), there may be a strong magnetic field interfering with the compass. Such interference may be caused by a magnetic antenna mount, magnetic note pad holder or a similar magnetic item. If the letter "C" should ever appear in the compass window, the mirror may need calibration. The mirror can be calibrated in one of two ways: 0 Drive the vehicle in circles at five mph (8 k d h ) or less until the display reads a direction, or Drive the vehicle on your everyday routine and after several turns the compass will become calibrated and will display a direction. 0 Compass Operation Press the COMP switch once briefly to turn the compass on or off. When the ignition and the compass feature are on, the compass will show two character boxes for approximately two seconds. After two seconds, the mirror will display the compass heading. When cleaning the mirror, use a paper towel or similar material dampened with glass cleaner. Do not spray glass cleaner directly on the mirror as that may cause the liquid cleaner to enter the mirror housing. Compass Variance 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, as during a long distance cross-country trip, it will be necessary to adjust for compass variance. Compass variance is the difference between earth's magnetic north and true geographic north. If not adjusted to account for compass variance, your compass could give false readings. 2-48