The HDLP SW fuse supplies voltage to the headlamp switch at all times through CKT 742 (RED). The headlamp switch includes a self-resetting circuit breaker. The circuit breaker opens if the headlamps draw too much current. Current flow is interrupted when the circuit breaker opens. When there is no current flow the circuit breaker cools off and 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. The signal disables DRL operation if the ignition switch is in RUN or START.

If the headlamp switch is in the HEAD position and the headlamp dimmer switch is in the LO position, voltage supplies through the normally closed contacts of the daytime running light relay, to the right and the left low beam headlamps.

When the headlamp switch is in the HEAD position and the headlamps 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 (Diesel) or G102 (Gasoline) constantly grounds the headlamps and the high beam indicator lamp.