Interior Lights Dimming Circuit Description

When the ignition switch is turned to the ON position, the dash integration module (DIM) sends a class 2 message to the instrument panel module (IPM), the instrument cluster (IPC), the radio, via power moding. In response to this message, each module will turn on its vacuum fluorescent (VF) displays at maximum brightness. The IPM turns on the VF display for the heater and A/C control head.

When the park lamps are turned on, battery voltage is supplied to the dash integration module (DIM) dimming circuit from the fuse in the rear fuse block. The DIM also sends a class 2 message to the IPM, indicating that the park lamps are on. The IP dimmer switch in the fog lamp switch is supplied a reference voltage from the IPM. It is supplied a ground from the IPM. The switch is a potentiometer that resistance varies as the switch is moved. The IPM receives an input voltage proportional to the resistance of the potentiometer.

When the park lamps are on and it is dark outside, the IPM sends a class 2 message to the DIM, the IPC, the drivers door module (DDM), and the radio indicating that the VF displays and incandescent lamps should be dimmed and the dimming level. The IPM, the IPC, and the radio, all dim their VF displays to match the current dimming level. The DIM sends a pulse width modulated (PWM) signal to the IP and console incandescent switch back lighting at the dimming level indicated by the IP dimmer switch. The DDM sends a simple bus interface (SBI) message to the RH front door module (RFDM), the LH rear door module (LRDM), and the RH rear door module (RRDM) indicating the dimming level. Each door module then sends a PWM signal to the incandescent switch back lighting the IP dimmer switch is moved from MINIMUM to MAXIMUM, all VF displays and incandescent switch back lighting dimming level changes from minimum intensity to maximum brightness in response to the IP dimmer switch.