GM Service Manual Online
For 1990-2009 cars only

Circuit Operation

The instrument panel dimmer switch controls the brightness of the incandescent lamps and vacuum fluorescent (VF) displays. The incandescent lamps are located in various components. . The VF displays are located in the radio and instrument cluster for a special equipment option (SEO).

Incandescent Dimming

A variable voltage signal produced by the instrument panel dimmer switch determines the brightness of the incandescent lamps.

Vacuum Fluorescent (VF) Dimming

The brightness of the vacuum fluorescent (VF) displays is controlled by the following signals:

    • The park lamps ON signal (circuit 308)
    • The VF dimming signal (circuit 230)

With the park lamps ON, the VF display of the radio, and the instrument cluster (SEO) will dim for low light viewing. When the park lamps ON signal is not present (park lamps OFF), the VF displays are at high brightness for daytime viewing. When the park lamps are ON, the instrument panel lamp dimmer switch provides a signal (VF dimming signal circuit 230) which controls the brightness of the VF displays when the instrument panel dimmer switch is adjusted.