For 1990-2009 cars

B+ is supplied to the solid state dimmer portion of the headlamp switch when the headlamp switch is in the PARK or HEAD position. The solid state dimmer supplies an adjustable amount of voltage to the instrument cluster, gauge cluster, and to other interior displays. The solid state dimmer is grounded to G103 through terminal 13 of the headlamp switch. All of the interior displays are grounded through either G103, G200, or G201.