Headlamp: Description and Operation

CIRCUIT OPERATION WITH TWILIGHT SENTINEL

The Twilight Sentinel System automatically turns the Headlights and Park Lights on and off according to light conditions. The system also keeps the lights on for an adjustable length of time after the driver turns the Ignition Switch OFF. The system can be turned off to give the driver manual control of the lights.

The Headlights receive battery voltage either through the Headlight Switch or through the Twilight Headlight Relay G. The other exterior lights are powered either through the Park Light Switch or through the Twilight Park Light Relay F.

The Twilight Sentinel System is controlled by the Delay Control and the Enable Switch. When the Control is moved away from OFF, the Twilight Enable Input to the Instrument Panel Cluster (IPC) is grounded.

With the Delay moved to the MAX position, approximately 4.5 volts is applied to the Twilight Delay Input to the Body Control Module (BCM). 180 seconds will be displayed for about 5 sections on the Driver Information Center (DIC).

When the Delay is adjusted for minimum time, the voltage applied to the BCM Twilight Delay Input is approximately 0.5 volts.

For the Twilight function, ambient light is sensed by the Twilight Photocell. The BCM Twilight Relay Control grounds the coils of the Twilight Headlight Relay and the Twilight Park Light Relay. The Relays energize and the Lo Beam Headlights, the Front Park and Marker Lights, the Console Ashtray Lights, and the Rear Side Marker, Tail, and License Lights turn on.