Headlamp Dimmer Switch: Testing and Inspection

Circuit Description:
The IPC reads the setting of the headlamp switch dimming potentiometer and provides a group of pulse width modulated (PWM) dimming signals to power the various lamps requiring dimming. There are three dimming circuits. In addition to the directly controlled lamps, the IPC broadcasts a Class 2 serial data bus VF dimming level message to the IRC, PHN and CCP. The CCP is found only with analog IPCs. The IPC internally controls the Cluster VF displays.
^ DIM-1
^ DIM-2
^ LED Dimming (analog Only)

The DIM-1 circuit (CKT 8) controls incandescent lamps in the following items:
^ IPC Backlighting
^ DIC Switch Assembly
^ CCP (analog IPC only)
^ Auxiliary Blower Switch
^ Radio (IRC)(except VF indications)
^ Steering Wheel Controls
^ Electronic PRNDL
^ Heated Seat Switches
^ Cigarette Lighter

The DIM-1 circuit will always be active whenever the Park Lamps are "ON."
The DIM-2 circuit (CKT 1244) controls incandescent lamps in the following items:
^ LF Window Switch Assembly
^ RF Window Switch Assembly
^ LR Window Switch Assembly
^ RR Window Switch Assembly
^ LF Flood Lamp
^ RF Flood Lamp
^ LR Flood Lamp
^ RR Flood Lamp
^ Headlamp Switch

The DIM-2 circuit will be active whenever the Park Lamps are ON" or the Illuminated Entry feature is "ON."
If the photocell is dark, the Twilight Sentinel switch is "OFF" and the ignition switch is in "RUN," the IPC will illuminate components on the DIM-2 circuit. The IPC will leave DIM-2 "ON" for 20 seconds after the key is cycled from "RUN."

The LED Dimming circuit (CKT 1382) controls the LED indicators in the optional Console Electronic PRNDL.

If the IPC has lost communication with the PZM, the IPC will turn "ON" backlighting (DIM-1, DIM-2 and LED dimming) if the photocell is dark.

The Incandescent dimming circuits (DIM-1 and DIM-2) are short circuit protected. If any short exists on the dimming circuit, all lighting on that circuit will turn "OFF."