Headlamp: Description and Operation

HEADLAMPS

The headlamps may be turned on in three different ways:
- The headlamp switch is placed in the ON position, for normal operation.
- The twilight delay switch placed in the ON position, for automatic lamp control (ALC).
- The twilight delay switch placed in the ON position, with the windshield wipers ON in daylight conditions, after a 6 second delay.

During ALC control the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. The dash integration module (DIM) provides battery positive voltage to the signal circuits of the headlamp switch. The circuits include the headlamp switch headlamps on signal and the flash to pass switch signal.

With the headlamp switch in the ON position, a ground path is available for the headlamp switch headlamps on signal circuit of the DIM through the headlamp switch. The DIM provides ground to either the headlamp low beam relay control circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay control has ground. The DIM supplies battery positive voltage to the relay control circuits, if the headlamps are necessary. The fuse block - underhood supplies battery positive voltage to both relay switch circuits. When the headlamp low beam relay control is energized, current flow is to both low beam fuses and to the low beam headlamps. The headlamps have ground at G103 and at G401. When the headlamp high beam relay control is energized, current flow is to both high beam fuses and to the high beam headlamps. The high beam circuit is divided into a left and right side circuit. The current flow of the left high beam is from the fuse to the left high beam lamp. From the lamp, the current flows to the normally-closed contact of the DRL relay to G103. The current flow of the right high beam is from the fuse to the right high beam lamp. From the lamp, the current flow is to ground at G401. When the headlamp dimmer switch lever is pulled toward the driver, the flash-to-pass switch closes. This grounds the DIM flash to pass switch signal. In response to this signal, the DIM energizes the HDLP HI BM relay. Both high beams remain on until the driver releases the switch handle. If the low beam headlamps were on during a flash-to-pass operation, the low beams remain on. The headlights may be switched to high beam with the forward movement of the dimmer switch lever.