Battery voltage is applied continuously to the headlamp switch through circuit 442. Voltage is applied to the headlamp dimmer switch and to the DRL control module through circuit 10, when the headlamp switch is in the HEAD position. The DRL control modules disengages the DRL function when circuit 10 provides voltage. Battery voltage is applied to the low beam headlamps through circuit 12 when the headlamp dimmer switch is placed in the LOW position. Battery voltage is applied to the high beam headlamps and to the DRL control module through circuit 11, when the headlamp dimmer switch is placed in the HIGH position. When the DRL control module receives the voltage on circuit 11, the DRL control module applies voltage to circuit 629. This turns on the high beam indicator in the instrument cluster.

The Daytime Running Lamps (DRL) control module is designed to automatically operate exterior lights depending on outside light conditions.

The DRL control module operates in 2 modes:

If the engine stalls with the DRL control module in the low light mode, the DRL control module turns OFF the headlamps while the engine is being cranked. The DRL control module turns ON the following lamps:

The following lamps operate in the usual manner:

The DRL control module receives voltage from fuse 33 through circuit 1439 and fuse 4 through circuit 41.

The following lamps may be operated manually at any time by using the headlamp and instrument panel lamp dimmer switch:

The DRL module does not operate if the system voltage is less than 9 volts or greater than 18 volts.

The DRL ambient light sensor is a light sensitive variable resistor. The DRL ambient light sensor's resistance decreases as the outside light intensity increases. Measuring the voltage drop across the DRL ambient light sensor and determining whether it should operate in the day mode or in the low light mode are the 2 basic features of the DRL ambient light sensor.

The DRL control module will not operate any headlamps or exterior lamps, if the park brake is applied before the ignition switch is turned to the RUN position. This allows the driver to start the vehicle and keep the headlamps OFF, as long as the park brake is applied. The DRL control module will activate the headlamps when the park brake is released with the ignition switch in the RUN position. This feature functions only when the park brake is applied before the ignition switch is turned to the RUN position. The headlamps will turn OFF, if the park brake is applied after the ignition switch is turned to the RUN position.

Connector C299 is disconnected to enable the functions of the display switch. The DRL lamps and the instrument cluster are turned OFF. When the display switch is turned to the OFF position. This enables the vehicle to have the engine running with all of the exterior and interior lights OFF. The headlamps and other exterior lamps are still controlled by the headlamp switch.