1998 GMC Suburban Owner's Manual - Page 123

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 elass cleanerdirectly on the mirror as that may cause the liquid cleaner to enter the mirror housing. L . Mirror Operation The right side of the switch located at the bottom of the mirror turns the electrochromic mirror on and off. The AUTO LED will come o n when the electrochromic mirror is turned on. To turn the mirror on, press and hold the MIRROR button for three seconds. The mirror will darken and remain dark until the button is released. To turn the mirror off, press and release the MIRROR button. Compass Calibration If, after two seconds, the display does not show a compass heading (-.N'' North, for example), there for may be a strong magnetic field interfering with the compass. Such interference may be c.aused 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. 2-45