Twilight Sentinel

The Twilight Sentinel System automatically turns the interior and exterior driving lamps on and off according to light conditions. The system also keeps the lamps on for a selected amount of time after the driver has parked and left the vehicle. The system can be turned off to give the driver manual control over the lamps.

The Twilight Sentinel will send a lamps "ON" signal to the Audible Warnings only if the Headlamp Switch is in the "PARK" or "HEAD" position.

Voltage is applied at all times through Fusible Link A to the Headlamp Switch terminal "K" (Chev) or terminal "F" Conn. C2 (Buick) and from the Headlamp Switch terminal "G" (Chev) or terminal "D" Conn. C2 (Buick) to the Headlamp Automatic Control Module connector C2 terminal "D."

When the Ignition Switch is in "RUN," voltage from LP Fuse #13 is applied to connector C1 terminal "E" of the Headlamp Automatic Control Module. Ground is supplied from G200.

As the intensity of light reaching the Headlamp Automatic Control Ambient Light Sensor decreases, the resistance of the Headlamp Automatic Control Ambient Light Sensor increases, When the Headlamp Automatic Control Module senses a high resistance in the Headlamp Automatic Control Ambient Light Sensor, the Headlamp Automatic Control Module energizes the Internal Head Relay. Battery voltage is applied through the closed contacts of the Head Relay to CKT 10. With the Dimmer Switch in "LO," the LO Beam Headlamps are ON." With the Dimmer Switch in "HI," the HI Beam Headlamps and Indicator are "ON." The Headlamp Automatic Control Module also energizes the Internal Park Relay, which applies battery voltage to CKT 9 and turns "ON" the Tail, Front Side Marker and Opera Lamps.

As the intensity of light reaching the Headlamp Automatic Control Ambient Light Sensor increases, the resistance of the Headlamp Automatic Control Ambient Light Sensor decreases. When the Headlamp Automatic Control Module senses a low resistance in the Headlamp Automatic Control Ambient Light Sensor, the Headlamp Automatic Control Module de-energizes the Internal Head Relay which turns the Headlights "OFF," and also de-energizes the Internal Park Relay which turns the Tail, Front Side Marker and Opera Lamps "OFF."

If the Ignition Switch is moved to "OFF," the Headlamp Automatic Control Module loses ignition voltage through I/P Fuse #13, and will cause a delay of 5 seconds to minutes and then turn the lamps off. This delay is set by changing the resistance of a delay rheostat in the Twilight Sentinel Switch.

When the Twilight Sentinel Switch is turned to "OFF," the path to ground at connector C1 terminal "A" at the Headlamp Automatic Control Module is opened. The system is turned off and the Headlamps will operate only by moving the Headlamp Switch to the "PARK" or "HEAD" position.

The Headlamp Automatic Control Module does not react instantly to ambient signals. Turn-on or turn-off is delayed from 15-20 seconds. This avoids needless operation for short periods of time.