Headlights Circuit Description

Headlights Circuit Description

The HEADLAMP fuse supplies voltage to the headlamp switch at all times through CKT 1042 (RED). The headlamp switch includes a self-resetting circuit breaker. The circuit breaker opens if the headlamps draw too much current. When the circuit breaker opens, the breaker interrupts the current flow. If there is no current flow, the circuit breaker cools off. The circuit breaker then resets automatically.

When the headlamp switch is in the HEAD position, voltage directs to the headlamp dimmer switch and the daytime running lights (DRL) control module. The headlamp dimmer switch directs voltage to either the low beam or the high beam headlamps depending on the position of the switch. The daytime running lights (DRL) control module receives the voltage at terminal D as a headlamps ON signal, which disables DRL operation if the ignition switch is in the RUN position, the BULB TEST or the START positions.

If the headlamp switch is in the HEAD position and the headlamp dimmer switch is in the LO position, voltage flows through the normally closed contacts of the daytime running light relay to the right and the left low beam headlamps. G101 constantly grounds the headlamps on diesel engines. G111 constantly grounds the headlamps on gasoline engines.

If the headlamp switch is in the HEAD position and the headlamp dimmer switch is in the HI position, voltage directs to the right and the left high beam headlamps. Voltage also directs to the (blue) high beam indicator lamp in the instrument cluster. G101 constantly grounds the headlamps and the high beam indicator lamp on diesel engines. G111 constantly grounds the headlamps and the high beam indicator lamp on gasoline engines.