GM Service Manual Online
For 1990-2009 cars only

While sitting in a comfortable driving position, adjust the mirror so you can see clearly behind the vehicle. Grip the mirror in the center to move it up and down or from side to side. The day/night control, located at the bottom of the mirror, lessens glare from the headlamps behind your vehicle when in the night position.

Pull the control lever for the night position; push it for the day position.