AM/FM Stereo
OPERATIONRadio Control Knob/VTF Display Illumination
The Instrument Panel Dimming Rheostat controls the brightness of the Electronic Radio control knob illumination bulbs, as well as the brightness of the Vacuum Tube Fluorescent (VTF) time/frequency display.
With the Ignition Switch in "ACC" or "RUN", voltage is present at the Instrument Panel Dimming Module through the RADIO Fuse and circuit 600 (DB/BK).
With the Main Light Switch turned to "OFF", the Instrument Panel Dimming Module applies battery voltage at C257, pin D, of the Electronic Radio, and the VTF display is illuminated at full brightness.
With the Main Light Switch in "PARK" or "HEAD", the Module: 1) reduces voltage to C257, pin D, to reduce VTF display illumination brightness, and 2) applies voltage to C257, pin E, to illuminate the Electronic Radio control knob illumination bulbs.
AM/FM Stereo
Voltage is present at C257, pin H, of the Electronic Radio at all times through the ROOM Fuse and circuit 330 (DB/R). This provides constant power to the Radio clock and station preset memory circuits.
With the Ignition Switch in "ACC" or "RUN", voltage is also present at C257, pin F, of the Electronic Radio through the RADIO Fuse and circuit 600 (DB/BK).
When the Electronic Radio is turned on, current flows through the RADIO Fuse, circuit 600 (DB/BK) and the Electronic Radio circuits to ground. The Radio turns on.