Caprice Wagon V8-350 5.7L (1994)
Twilight Sentinel: Description and Operation
The Twilight Sentinel System automatically turns the interior and exterior driving lights on and off according to light conditions. The system also keeps
the lights 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 lights.
The Twilight Sentinel will send a lights "ON" signal to the Warning Alarm 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" (Chevy) or terminal "F" Conn. C2 (Buick) and from the
Headlamp switch terminal "G" (Chevy) or terminal "D" Conn. C2 (Buick) to the Headlamp Auto Control Module connector C2 terminal "D".
When the Ignition Switch is in "RUN," voltage from I/P Fuse #13 is applied to connector C1 terminal "E" of the Headlamp Auto Control Module.
Ground is supplied from G200.
As the intensity of light reaching the Headlamp Auto Control Ambient Light Sensor decreases, the resistance of the Headlamp Auto Control Ambient
Light Sensor increases. When the Headlamp Auto Control Module senses a high resistance in the Headlamp Auto Control Ambient Light Sensor, the
Headlamp Auto Control Module energizes the Internal Head Relay. Battery voltage is applied through the closed contacts of the Head Relay to CKT 10.
With the Headlamp Dimmer Switch in "LO," the LO Beam Headlights are "ON." With the Headlamp Dimmer Switch in "HI," the HI Beam Headlights
and Indicator are "ON." The Headlamp Auto 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 Auto Control Ambient Light Sensor increases, the resistance of the Headlamp Auto Control Ambient
Light Sensor decreases. When the Headlamp Auto Control Module senses a low resistance in the Headlamp Auto Control Ambient Light Sensor, the
Headlamp Auto 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 Auto Control Module loses ignition voltage through I/P Fuse #13, and will cause a delay of 5
seconds to 3 minutes and then turn the lights 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 Auto 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 Auto 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.
