Circuit Operation - Radio

The Radio receives battery voltage at all times on CKT 640 through Fuse 10 to keep clock and preset station memory alive when the Ignition is OFF. With the Ignition Switch in ACCY or RUN, voltage is applied to CKT 43 through Fuse 38 to enable Radio operation. The Radio is grounded through CKT 351. When the Ignition is in RUN or ACCY, the vacuum fluorescent display illuminates to display the time or Radio frequency setting.

The Radio illumination is controlled by the Instrument Panel Lamp Dimmer. When the Headlamp Switch is in PARK or HEAD, voltage is applied through the Dimmer Control and CKT 230 to the Radio panel lamp and the internal circuitry. When the Headlamp Switch is switched to PARK or HEAD, voltage is applied through CKT 308 to the Radio, signaling the internal circuitry to adjust the brightness of the vacuum fluorescent display to a level determined by the voltage of CKT 230.