GM Service Manual Online
For 1990-2009 cars only

Circuit Operation

The IP dimmer switch controls the brightness of the following components:

    • The incandescent illumination lamps of the instrument cluster.
    • The vacuum fluorescent  (VF) displays of the radio.

Incandescent Dimming

When the headlamp switch is in the PARK position or the HEAD position or the vehicle is in a low light condition with DRL active, voltage is applied through circuit  9 to the IP dimmer switch. Voltage from the IP dimmer switch is applied through circuit  44, the IP dimmer fuse and circuit 8 to the incandescent lamps. Turning the IP dimmer switch changes the voltage on circuit  8 which varies the intensity of the lamps.

Vacuum Fluorescent Dimming

When the headlamp switch is in the PARK position or the HEAD position or the vehicle is in a low light condition with DRL active, voltage is applied through circuit  9 to the IP dimmer switch. Voltage from the IP dimmer switch is applied through circuit  44, the IP dimmer fuse and circuit 8 to the radio VF display. The radio VF display dims for night viewing. Turning the IP dimmer switch changes the voltage on circuit  8 which varies the intensity of the radio VF display.