Circuit Operation - Dim Illumination Lamps

The I/P Dimmer controls the brightness of the illumination bulbs by using a Pulse Width Modulated (PWM) ground for all the illumination bulbs (circuit 44). When the headlamp switch is in the park or help position all of the illumination bulbs and the I/P dimmer receive battery voltage on circuit 9. When the I/P dimmer receives the battery voltage at pin C (circuit 9) the internal PWM control circuitry turns on. The I/P dimmer now modulates the ground (circuit 44) of all the illumination bulbs by increasing or decreasing the duty cycle based on the position of the I/P dimmer knob. When the I/P dimmer knob is rotated to the LO position (full counter-clockwise) the duty cycle is approximately 20% and when rotated to the HI position (full clockwise) the duty cycle is 100%.