GM Service Manual Online
For 1990-2009 cars only

Automatic Day-Night Mirror System Components

The automatic day-night mirror system consist of the following components:

    • Inside rearview mirror
    • Passenger outside mirror with the automatic day-night feature

Automatic Day-Night Mirror Operation

With the ignition switch in the ON position, ignition 3 voltage is supplied through the HVAC 1 fuse to the inside rearview mirror. The inside rearview mirror uses 2 photocell sensors in order to determine light conditions in the front and the back of the vehicle. At night, with the automatic day-night feature enabled, the mirror automatically darken to reduce the glare from the headlamps from behind. In the daytime, the mirror is in a normal state. With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as an input to the inside rearview mirror. The mirror will gradually change to a normal state as a result of the backup lamp supply voltage input. Ground for the inside rearview mirror is provided by G202.

The inside rearview mirror supplies a low reference circuit and a signal circuit to the passenger outside rearview mirror. Refer to Outside Mirror Description and Operation in Doors for further description and operation of the driver outside rearview mirror.

Automatic Day-Night Mirror Switches (w/o OnStar®)

The automatic day-night mirror has two switches that perform the following functions:

    • The AUTO switch is used to enable the automatic day-night feature of the mirror. With the ignition in the ON position, depress the AUTO switch to enable the automatic day-night feature of the mirror. A green indicator will illuminate on the mirror when the automatic day-night feature is enabled.
    • The OFF switch is used to disable the automatic day-night feature of the mirror. To disable the automatic day-night feature of the mirror, depress the OFF switch.

Automatic Day-Night Mirror Switch (w/OnStar®)


Object Number: 671554  Size: SH

This is the on/off switch for the automatic day-night mirror. The on/off switch is used to enable or disable the automatic day-night feature of the mirror. With the ignition in the ON position, depress the on/off switch to enable the automatic day-night feature of the mirror. A green indicator will illuminate on the mirror when the automatic day-night feature is enabled. To disable the automatic day-night feature of the mirror, depress the on/off switch.