Circuit Operation - Interior Lights Dimming

The I/P Dimmer Switch controls the brightness of the incandescent lamps and Vacuum Fluorescent (VF) displays. The incandescent lamps are located in various components (see schematics) and the VF displays are located in the Radio.

Incandescent Dimming
The brightness of the incandescent lamps is determined by a variable voltage signal produced by the Headlamp Switch through CKT 8.

VF Dimming
The brightness of the VF Displays is controlled by two signals: the VF Dim Displays Signal (CKT 308) and the VF Dimming Signal (CKT 230). With the Park Lamps ON (VF Dim displays CKT 308) the VF display of the Radio will dim for night-time viewing. When the VF Dim Displays Signal is not present (Park Lamps OFF), the VF displays are at high brightness for daytime viewing. When the Park Lamps are ON, the Headlamp Switch provides a Pulse Width Modulated (PWM) signal (VF Dimming Signal CKT 230) which controls the brightness of the VF displays when the I/P Dimmer Switch is adjusted.

Special Equipment Option (SEO) VF Dimming
The VF Displays of the Digital Speedometer and the Radio can be step dimmed to a Night Mode by the VF Dim Displays Signals from the Headlamp Switch (CKT 308) or the Display Switch (CKT 328). The SEO Diode serves to prevent backfeeding from CKT 308 when the Headlamp Switch is ON and the Display Switch is OFF The SEO Diode serves to prevent backfeeding from CKT 308 to CKT 39 if the Display Switch and the Headlamp Switch are both ON with the Ignition OFF.