Headlamp: Description and Operation

HEADLAMPS

The turn signal/headlamp switch lever is located on the left side of the steering column. A twist-type knob on the end of the switch lever controls the operation of the parking lamps and headlamps. A solid tone will sound as a reminder if you open the drivers door with the key out of the ignition and the park lamps or the headlamps on. When either the parking lamps or headlamps are activated, the following lamps also illuminate:
- The tail lamps
- The rear license plate lamps
- The instrument cluster assembly lamps
- The cigar lighter lamp
- The I/P ashtray lamp
- The manual selector lever lamp

Voltage is applied continuously to the HLP relay pins 2 and 4 through the 30 A H MAIN fuse. The coil is energized when the daytime running lamps control module is active in normal park or headlamp operation. When the coils are energized current flows through the HLP R and HLP L fuses and then into the lamps mentioned above.

The instrument panel and instrument cluster assembly illumination lamps intensity is controlled by the I/P lamp dimmer, instead of remaining at 100 percent.

Low Beam System Operation
The headlamps may be turned on two different ways. First, when the end of the of the turn signal/headlamp switch lever is turned to the second detent position, the headlamps will illuminate. A ground signal is provided to the DRL control module. The module then provides a ground path to the coils of the HLP relay. Since the head relay is provided with battery voltage to both the contacts and the coil, the coil becomes energized and closes the contacts providing voltage to the DIM relay. With voltage and ground provided, the low beam lamps light. Second, with the switch in the OFF position, for automatic lamp control (ALC). During ALC the headlamps will be in one of the following modes of operation:
- Daytime running lamp (DRL) operation in daylight conditions, refer to DRL below for the operation of the circuit.
- Low beam headlamp operation in low light conditions. When the ambient light sensor senses a low light condition for approximately 15 seconds, it will cancel DRL operation and turn on the headlamps at 100 percent intensity. A path to ground is provided to the coil of the HLP relay. With a direct path to ground provided to the headlamps though the DRL control module, the headlamps will light at 100 percent intensity.

High Beam System Operation
The high-beam headlamp operation is controlled using the turn signal/headlamp switch lever on the steering column. In order to change headlamp operation from low-beam to high-beam, push the switch lever toward the instrument panel (until the detent is felt) and release. With the switch lever in the high beam position, ground is provided to the DRL control module through the turn signal/headlamp switch and splice pack 200 to G200. The DRL control module provides a ground to the coil of the dimmer relay. Since voltage is being applied to the dimmer relay coil, it becomes energized. Voltage is then applied through the closed contacts of the dimmer relay and the to the high beam lamps in the headlamps. Since ground is provided to the headlamps through the closed contacts of the energized DIM relay, the high beam lamps light. The high-beam indicator (blue) in the instrument cluster will light during high-beam headlamp operation. In order to change headlamp operation back to low-beam operation, pull the turn signal switch lever toward the driver (until the detent is felt) and release.

Flash-to-pass System Operation
The Flash-to-Pass feature allows the driver to signal the driver of another vehicle his intention to pass. This is achieved by pulling the lever toward the driver, which will cause the high beam operation to illuminate until the lever is released. The operation of the headlamps with the turn signal/headlamp switch in flash-to-pass mode is the same as the operation of the switch in the high beam mode except the lamps will turn off when the switch is released.

Refer to Headlamp Switch Replacement for turn signal/headlamp switch removal and installation procedures.