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.

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 nighttime 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 "SPEEDO DIM" Switch (CKT 328). The I/P Dimmer Switch Diode serves to prevent backfeeding from CKT 1244 when the Headlamp Switch is "OFF" and the "SPEEDO DIM" Switch is "ON." The SEO Switch Panel Diode serves to prevent backfeeding from CKT 1244 to CKT 39 if the "SPEEDO DIM" Switch and the Headlamp Switch are both "ON" with the Ignition "OFF."