Dimmer Switch: Description and Operation

Voltage is applied at all times from I/P Fuse Block Fuse 14 to the Lamp Switch. When the Lamp Switch is in either the PARK or HEAD position, voltage is applied through I/P Fuse Block Fuse 25 to the dimming rheostat and then as a variable voltage to the instrument panel. Adjusting the dimming rheostat changes the current supplied to the instrument panel incandescent lamps, allowing the lamps to dim or brighten.
The vacuum fluorescent (VF) displays in the Digital Cluster, Radio, Climate Control Panel, and Fuel Data Center receive a separate Body Computer Module (BCM) input to control their dimming. The BCM uses the variable voltage output from the dimming rheostat as an input. Within the BCM there is a regulator which provides 16 volts to the VF displays. This regulator also provides the variable 16 volt input to the ECC Power Module for blower speed control. This 16 volt supply and the variable VF dimming control signal control the VF displays.