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For 1990-2009 cars only

Inside Rearview Mirror with the Automatic Day-Night Feature System Components

The automatic day-night feature system consist of an inside rearview mirror.

Power and Ground of the Inside Rearview Mirror

    • With the ignition ON, ignition voltage is supplied to the mirror from the A/C CRUISE fuse in the left I/P junction block.
    • Ground for the mirror is provided by G302.

Inside Rearview Mirror with the Automatic Day-Night Feature System Operation

The inside rearview mirror uses 2 photocell sensors. One sensor is the headlight sensor, located on the rear side of the mirror. The headlight sensor is used to determine light conditions present at the mirror face. The other sensor is the ambient light sensor, located on the front of the mirror or windshield side. The ambient light sensor is used to determine light conditions present at the mirror. With automatic day-night feature enabled, the mirror uses ambient light sensor to determine the exterior light condition. With a low light condition detected, and a high light condition from behind at the headlight sensor, the inside rearview mirror will automatically darken the face of the mirror.

In the daytime, the mirror is in a normal state because of the high light condition that is indicated by the ambient light sensor. With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as an input to the inside rearview mirror. In night time conditions only, the mirror monitors this input to disable the automatic day-night feature which allows the face to gradually change to a normal state. This allows the driver to see objects in the mirror clearly when backing up.

Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature

The inside rearview mirror has three switches that perform the following functions:

    • The switch at the center of the mirror is used to enable or disable the automatic day-night feature. With the ignition in the ON position, depress the 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 switch again.
    • The other two switches are for turning the map lights on the mirror ON and OFF.

Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature without Compass with OnStar®

The inside rearview mirror has 4 switches that perform the following functions:

    • The on/off switch for automatic day-night feature of the inside rearview mirror is located at the left side of the 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.
    • The three switches on the right side of the mirror are for OnStar® operation. For more information, refer to OnStar Description and Operation in Cellular Communication.