2008 GMC Envoy Owner's Manual - Page 116

Automatic Dimming Mirror Operation The automatic dimming mirror function is turned on automatically each time the ignition is started. To operate the automatic dimming mirror, do the following: 1. Make sure the green indicator light, located to the left of the on/off button, is lit. If it's not, press and hold the on/off button until the green light comes on, indicating that the mirror is in automatic dimming mode. 2. Turn off the automatic dimming mirror function by pressing and holding the on/off button until the green indicator light turns off. To adjust between Fahrenheit and Celsius, do the following: 1. Press and hold the on/off button until either a flashing F or C appears. 2. Press the button again to change the display to the desired unit of measurement. After approximately four seconds of inactivity, the new unit will be locked in and the display will return. If an abnormal temperature reading is displayed for an extended period of time, please consult your dealer. Under certain circumstances, a delay in updating the temperature is normal. Temperature and Compass Display Press the on/off button, located to the far left, briefly to turn the compass/temperature display on or off. If the display reads CAL, you will need to calibrate the compass. For more information on calibration, see below. 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 of 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. 2-42