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 your vehicle. Grip the mirror in the center to move it up or down and side to side. The control at the bottom of the mirror is the day/night feature that allows adjustment to the mirror so that the glare of headlamps from behind is reduced. Push the control for daytime use; pull it for night use.