Headlamp: Description and Operation

Headlamps

Voltage is supplied to the Light Switch at all times The Light Switch includes a Self-Resetting Circuit Breaker. The Circuit Breaker opens when the Headlamp circuit draws too much current. When the Circuit Breaker opens, it interrupts the current flow. With no current flow, the Circuit Breaker cools off and resets automatically. When the Light Switch is in HEAD, the Headlamp Dimmer Switch directs voltage to either the Low Beams or High Beams. The High Beam Indicator also receives voltage along with the High Beams.

Daytime Running Lamps

Voltage is supplied to the Daytime Running Lamps Relay at all times through the ORN (340) wire from the DRL Fuse and when the Ignition Switch is placed in RUN through the PNK/BLK (39) wire from the GAGES Fuse. The relay provides voltage to the LH High Beam through the DK BLU/WHT (593) wire. This wire also becomes the ground wire when the Headlamps are operating normally.
Voltage is supplied to the Daytime Running Lamps Module (Canadian only) when the Ignition Switch is placed in RUN through the BRN (50) wire from the A/C HTR Fuse for Utility and Suburban vehicles and through the PNK/BLK (39) wire and the GAGES Fuse for Pickup vehicles. When the Ignition Switch is placed in RUN, the voltage from the relay is provided a ground path through the LT GRN (11) wire through the module. This enables the relay to provide voltage to the High Beam Lamps in series causing the lamps to share the voltage resulting in the lamps operating at half intensity.
The module will not enable the relay if the Light Switch is in the ON position or the Park Brake Switch is ON.
The High Beam Indicator also receives voltage from the module when the Headlamp Dimmer Switch is in the High position.