Panel Lamps Dimmer Circuit

The panel lamps dimmer circuit actually includes several circuits. These circuits control the back lighting illumination and dimming level of the headlamp switch, the heater-air conditioner controls, the instrument panel switch pod, the four-wheel drive selector switch, the automatic transmission gear selector bezel lamp, the front door map pocket and remote inside handle lamps, as well as the center floor console cup holder and forward storage compartment lamps. All lamps in the panel lamps dimmer circuits are provided a path to ground at all times through a hard wired ground circuit. These lamps are illuminated by a 12-volt Pulse Width Modulated (PWM) output of the EMIC through several panel lamps dimmer circuits.

This shared PWM output synchronizes the selected illumination intensity level of all the lamps in the panel lamps dimmer circuits. The EMIC uses hard wired inputs from the rotary exterior lighting control knob and interior lighting thumbwheel of the headlamp switch to determine when the exterior lighting is turned ON and the dimming level selection. Then the EMIC provides the appropriate PWM outputs through the panel lamps dimmer circuits as well as electronic dimming level  messages over the CAN data bus to other electronic modules in the vehicle.

The EMIC, the instrument panel switch pod and the radio use the electronic dimming level  messages to control the illumination intensity of their own back lighting, controls and display units. In addition, when the interior lighting thumbwheel of the headlamp switch is moved to the PARADE (or funeral) mode detent position, all of the electronic display units are illuminated at their full intensity levels for increased visibility when the vehicle is driven during daylight hours with the exterior lighting turned ON. The PARADE mode has no effect on the illumination intensity of incandescent panel lamps.