The instrument panel dimming system provides a variable level of illumination at the driver indication and the controls. The system works with both incandescent lamps and with florescent displays, as in the PRNDL display at the instrument cluster. Adjusting the position of the dimmer thumbwheel on the instrument panel (IP) dimmer switch supplies a variable voltage to the system lamps and the system components.

Voltage is available at all times at PARK LPS fuse 9. This voltage is available to the headlamp switch through CKT 240 (ORN). With the headlamp switch in either the park lamps or the headlamps position, voltage is available to the rheostat of the IP dimmer switch. The voltage supplied through CKT 44 (DK GRN) to ILLUM fuse 14 depends on the position of the dimmer thumbwheel. This voltage is then available to the system lamps and the system components through CKT 8 (GRY). The illumination lamps in the instrument cluster and the heater and air conditioning (A/C) controller have ground in CKT 150 (BLK) at ground G201. The illumination lamps in the front auxiliary heating and/or A/C components, as equipped, have ground in CKT 150 (BLK) at ground G400. These lamps respond directly to the voltage supplied in order to produce variable levels of illumination.

The radio and instrument cluster's PRNDL and odometer indications do not operate directly from the incoming voltage in CKT 8 (GRY). These components use the variable voltage as a setpoint signal in order to adjust the component's illumination as powered from another circuit. The radio's illumination circuit has power from RADIO I fuse 17 through CKT 43 (YEL). The radio's illumination circuit has ground in CKT 150 (BLK) at ground G201. The instrument cluster PRNDL and odometer illumination circuits have power from TRANS fuse 20 through CKT 1020 (PNK). The instrument cluster's electronic ground is at ground G101 through CKT 451 (BLK/WHT). With no voltage in CKT 8 (GRY), the illumination levels for these components have settings for daytime brightness. With voltage in CKT 8 (GRY), solid state electronics set the brightness in proportion to the voltage set by the dimmer position.

Overriding the instrument panel dimming voltage level to the radio and to the instrument cluster's PRNDL and odometer indications and restoration to full brilliance even though the park lamps or the headlamps are in operation is possible. In order to accomplish the override, place the IP dimmer switch's thumbwheel adjustment in the parade mode detent position. (The detent position is shown as the parade mode switch.) With the switch in the parade mode detent, voltage from PARK LPS fuse 9 is available in CKT 1382 (PPL/WHT). With voltage present in CKT 1382 (PPL/WHT) at the radio or at the instrument cluster, the illumination levels are at full brightness for the following components: