System Description

Voltage is present at the coil and contacts of the Park Lamp Relay at all times through the TAIL Fuse.

Electronic Radio Illumination

With the Ignition Switch in ACC or RUN, voltage is present at pin H of the Instrument Panel Dimming Rheostat through the RADIO Fuse. With the Main Light Switch in OFF, the Park Lamp Relay is not energized and voltage is NOT present at pin D of the Instrument Panel Dimming Rheostat. With this input information, the Rheostat applies voltage at pin F to power the Electronic Radio LCD at full brightness for daytime visibility.

If the Main Light Switch is placed in PARK or HEAD, the Park Lamp Relay is energized and voltage is now present at pin D of the Instrument Panel Dimming Rheostat. The Rheostat now reduces voltage at pin F to dim the LCD display. At the same time, the Rheostat applies voltage at pin B to illuminate the Electronic Radio control knobs, marking them visible at night. The voltage applied to pin B is variable and determined by the position of the Rheostat dial.

All Other Illumination Bulbs

With the Ignition Switch in ACC or RUN, voltage is present at the Instrument Panel Dimming Rheostat through the RADIO Fuse.

With the Main Light Switch in PARK or HEAD, the Park Lamp Relay is energized and voltage is present at all instrument, switch, and control illumination bulbs through circuit 301 (R/BK). Voltage is also present at pin D of the Instrument Panel Dimming Rheostat through the same circuit. Since all illumination bulbs are grounded through circuit 305 (R) and the Rheostat, the Rheostat can determine bulb brightness by varying the resistance between pin A and G. The resistance between pins A and G is determined by the position of the Rheostat dial.