Each headlamp is individually fused so that battery voltage is applied to the individual lamps at all times through circuit 1640 for the LH headlamps and through circuit 1740 for the RH headlamps. When the headlamp switch is in HEAD, the ground is applied directly to headlamp switch through circuit 1750. When the headlamp switch is placed in LOW, ground is applied to the low beam headlamps through circuit 1201. When the headlamp switch is placed in HIGH, ground is applied to the high beam lamps and to the high beam indicator through circuit 1200. The high beam indicator is fused so that battery voltage is applied at all times through circuit 640.

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 two modes: the day mode and the night mode. In the day mode, the DRL ambient light sensor senses daylight then the DRL control module turns on the front turn lamps (non-flashing) under the following conditions:

In the night mode, the DRL ambient light sensor senses darkness then turns off the front turn lamps and turns on the headlamps through circuit 10 and turns on the park, side marker, license, and tail lamps. If the engine should stall with the DRL control module in the night mode, the DRL control module will turn off the headlamps and leave the side marker, park, license and tail lamps are on while the engine is being cranked. The headlamp and instrument panel lamp dimmer switch operates as usual.

The DRL control module receives voltage from the DRL fuse through circuit 1239 and the HVAC fuse through circuit 41. The park lamps and/or the headlamps may be operated manually at any time by using the headlamp switch. The DRL module will not operate if the system voltage is less then 9 volts or greater than 18 volts.

The DRL ambient light sensor is a light sensitive variable resistor. Its resistance decreases as outside light intensity increases. The DRL control module measures the voltage drop across the DRL ambient light sensor and determines whether it should operate in the day mode or night mode.

If the park brake is applied before the ignition switch is turned on, the DRL control module will not operate any headlamps or exterior lamps. This allows the operator to start the vehicle and keep the headlamps off, as long as the park brake is applied. When the park brake is released with the ignition switch on, the DRL control module will activate the headlamps. This feature will only function when the park brake is applied before the ignition switch is turned on. If the park brake is applied after the ignition switch is turned on, the headlamps will not turn off.