Instrument Panel Dimming

The vacuum fluorescent displays are dimmed and the incandescent (panel) lights are turned on only if the Park Lights or the Headlights are on, ambient light is low and the Ignition Switch is in RUN. The dimming level (brightness) of the vacuum fluorescent displays and the incandescent (panel) lights is determined by the Instrument Panel Dimming Control setting at BCM terminal 3C8. Park Light and Headlight status is determined by the BCM at terminal 3D12, and ambient light conditions are determined by the Twilight Photocell at BCM terminal 3C7. In high ambient light with the Ignition Switch in RUN, all vacuum fluorescent displays are at full brightness and all incandescent (panel) lights are off regardless of the Park Lights or Headlight status.

The BCM determines the dimming level and generates two outputs. One output is pulse-width modulated and dims the vacuum fluorescent displays of the HVAC Control Panel, Radio and Compact Disc or Remote Cassette Tape Player through circuit 724 at BCM terminal 1C4. The other output is dimming information which is sent through the serial data line to the Instrument Panel Cluster (IPC). The IPC then generates a pulse-width modulated signal to its vacuum fluorescent drivers and also generates a pulse-width modulated signal to the incandescent (panel) lights through circuit 8 at terminal C11.