2008 GMC Sierra 1500 Pickup Owner's Manual - Page 113

Mirrors Automatic Dimming Rearview Mirror with OnStar®, Compass and Temperature Display Your vehicle may have this feature. When on, an automatic dimming inside rearview mirror automatically dims to the proper level to minimize glare from lights behind you after dark. The mirror also includes a dual display in the upper right corner of the mirror face. The compass reading and the outside temperature will both appear in the display at the same time. To adjust between Fahrenheit and Celsius: 1. Press and hold the on/off button for approximately four seconds 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 compass/temperature display will return. If an abnormal temperature reading is displayed for an extended period of time, please see your dealer. Under certain circumstances, a delay in updating the temperature is normal. 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 for approximately six seconds 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 for approximately six seconds, until the green indicator light turns off. P (On/Off): This is the on/off button. 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 "Compass Calibration" following. 2-37