The daytime running lamps (DRL) control module and the turn signal/headlamp switch control the headlamps. The H/L, L and H/L, R Fuses supply voltage to the headlamps, the high beam indicator and the headlamp relay through the DRL diode at all times. With the switch in the HEAD position and the dimmer switch in low, ground is provided to the low beam filaments through the dimmer switch and the closed contacts of the Headlamp Relay to G200. The low beam filaments will light when the ground is supplied.
With the dimmer switch in the high position, the high beam filaments in the headlamps ground through the dimmer switch, through the closed contacts of the headlamp relay to G200. The high beam filaments will light when the ground is supplied. The ground path for the high beam Indicator is the same as the high beam filaments.
With the dimmer switch in the pass position, the high beam filaments in the headlamps ground through the dimmer switch to G200. The high beam filaments will light with ground supplied. The ground path for the high beam Indicator is the same as the high beam filaments.
The ON or START position of the ignition switch applies voltage to the DRL control module through the IG Fuse. The DRL control module permanently grounds to G200. The following conditions are required before the DRL system will work properly:
| • | Disengage the parking brake. |
| • | The DRL control module must not receive a ground signal from the generator. |
| A ground signal from the generator indicates the engine is not operating and the generator is not charging the battery. |
| • | The turn signal/headlamp switch is either in the OFF or in the PARK position. |
| • | The ambient light sensor must not sense a low light condition. |
When the parking brake engages, the parking brake switch closes. The switch provides a ground to the DRL control module. The ground disables the DRL operation. When the generator is not operating, a switch in the generator closes. The switch provides a ground to the DRL control module. The ground disables the DRL operation. When the turn signal/headlamp switch is in the HEAD position, a ground is provided to the DRL control module. This signal disables DRL operation.
When all of the conditions for DRL operation are met, the DRL control module provides a ground for the low beam filaments in the headlamps through the DRL control module to G200. The H/L, L and H/L, R Fuses supply the voltage to the headlamps at all times. The low beam filaments will light at 80 percent intensity.
The ON position of the ignition switch applies voltage to the ambient light sensor through the DEF Fuse. The ambient light sensor permanently grounds to G200. When the ambient light sensor senses a low light condition, a path to ground is provided to the headlamp relay through the ambient light sensor. This same signal is also provided to the DRL control module and disables DRL operation. Voltage is provided from the H/L Fuses, through the DRL diode to the coil of the headlamp relay. The relay contacts close providing a ground to the headlamps. The headlamps will light at full intensity.
