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
    • Compass
    • Driver outside rearview mirror

Automatic Day-Night Mirror Operation

With the ignition switch in the ON position, accessory voltage is supplied through the ACC 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 darkens 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 mirrors 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 G400.

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

Compass

The electronic compass includes a magnetic field sensor and a microprocessor. The microprocessor receives inputs from the sensor, processes these inputs, and provides a heading on the compass display.

Automatic Day-Night Mirror Switch with 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 perform the following functions:

    • To enable or disable the automatic day-night feature of the mirror. With the ignition in the ON position, depress and hold the on/off switch for 4 seconds 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 and hold the on/off switch for 4 seconds.
    • To turn the compass on and off. With the ignition in the ON position, depress the on/off switch to turn the compass on. Depress the on/off switch again to turn the compass off. The on/off switch is also used to place the compass into a calibration or zone mode. For more information, refer to Compass Calibration and Magnetic Variance .