Headlamp: Description and Operation

HEADLAMP SYSTEM
The headlamp system is controlled completely by the Body Control Module (BCM). The BCM controls the Park lamps, Headlamps, and Front Fog Lamps using relays located in the Junction Block. Three wires are connected between the headlamp switch and the BCM. The first wire contains information regarding the position of the headlamp switch (Off, Automatic Headlamps, Automatic Headlamp switch fog, Park with Fog, Head, or Head with Fog Lamps). The second wire contains information regarding the position of the dimmer switch (Dome Lamp, Daytime Brightness, or Dimming Level). The third wire is a dedicated signal return (ground) wire.

The headlamp system will default to the head- lamps ON position when the ignition switch is ON, or when an open/short circuit failure occurs on the headlamp switch input. The system will return to normal operation when the open or short is repaired. A fault will be reported by the BCM when a failure occurs on the dimmer or headlamp switch input.The dimmer system will default to Daytime Brightness when an open or a short occurs on the dimmer switch input.

The BCM will turn OFF the exterior lamps if they are left ON with the ignition switch OFF for more than ten minutes. This feature prevents the vehicle battery from being discharged when the vehicle lights have been left ON.

AUTO HEADLAMP SYSTEM
The Automatic Headlamp system turns the instrumentation and exterior illumination lamps ON when the ambient light levels are low and OFF when light levels are high.

Automatic headlamps are controlled by the Body Control Module (BCM). With the headlamp switch in the AUTO position (Automatic mode). The BCM will control the headlamp, parking, side marker, tail and instrumentation lamps based on ambient light levels. Ambient light levels are monitored by the BCM using the automatic temperature control system Sun Sensor, located on the top of the instrument panel cover. Ambient light readings are averaged to limit cycling the lamps ON and OFF when passing through areas with varying light levels. The automatic headlamps will only function when the engine is running. When the headlamp switch is in the AUTO position, the Headlamp Time Delay system will function when the ignition is switched OFF

HEADLAMPS ON WITH WIPERS
For vehicles equipped with the Automatic Headlamp System, the instrumentation and exterior illumination lamps will be turned ON when the headlamp switch is in the AUTO position and the windshield wipers have been in the intermittent, low or high mode of operation for more than ten seconds. When the windshield wipers are turned OFF the Body Control Module will determine if the instrumentation and exterior illumination lamps should remain ON base upon the current ambient light level.

LAMP SYSTEMS
Vehicles use lighting on the interior and exterior of the vehicle for illuminating and indicating purposes. Lighting circuits are protected by fuses or circuit breakers. Lighting circuits require an overload protected power source, on/off device, lamps and body ground to operate properly. Plastic lamp sockets require a wire in the harness to supply body ground to the lamp socket. Lamp sockets that are exposed to moisture should be coated with Mopar Multi purpose Grease or equivalent to avoid corrosion. If a socket has become corroded, clean socket and bulb base with abrasive fiber sanding pad or metallic bristle brush. Replace sockets and bulbs that are deformed from corrosion that could prevent a continuous body ground.

Wire connectors can make intermittent contact or become corroded. Before coupling wire connectors, inspect the terminals inside the connector. Male terminals should not be bent or disengaged from the insulator. Female terminals should not be sprung open or disengaged from the insulator. Bent and sprung terminals can be repaired using needle nose pliers and pick tool. Corroded terminals appear chalky or green. Corroded terminals should be replaced to avoid recurrence of the problem symptoms. Wire connector terminals should be coated with Mopar Multi purpose Grease or equivalent to avoid corrosion.

Begin electrical system failure diagnosis by testing related fuses and circuit breakers in the fuse block and engine compartment. Verify that bulbs are in good condition and test continuity of the circuit ground. Refer to Wiring Diagrams, for component location and circuit information.

HIGH INTENSITY DISCHARGE HEADLAMPS - 300M SPECIAL
This vehicle is equipped with High Intensity Discharge Headlamps (RID). The HID type lamp is used in place of the conventional halogen low beam lamp. High beam lamps remain the same halogen type.

Fig.23 HID System Components:

There are three components in the HID system, the ballast module (attached to the bottom of the headlamp unit), the igniter (plugs into the ballast module), and the lamp itself (part of the igniter assembly and only replaceable with the igniter).HID lamps get their name from the intense white light produced by the electrical discharge. The light produced by the HID lamps appears as a white color as opposed to the yellow color of the standard halogen lamps.

HID lighting provides about three times the light output of standard halogen lamps while using less energy The lamps are also designed to last 10 times longer than standard halogen lamps.

High Intensity Discharge Headlamps (HID) rely on an electrical charge to ignite xenon gas contained in a sealed beam lamp. The HID lamps are similar in operation to common vapor filled street (halogen) lamps. Instead of using a filament to produce light, the gas inside the lamp is ignited by creating an arc between two electrodes.

The color of the light source is classified as its color temperature. As the color temperature increases, the color of the light moves from yellow to white to blue-white. The light produced by the HID lamps appears as a white color as opposed to the yellow color of the standard (halogen) lamps. HID lamps provide light as a higher color temperature than standard halogen lamps.

Color Temperature:

For the color temperature of different lamp types, refer to the COLOR TEMPERATURE table. As a point of reference, typical sunlight at noon has a color temperature of 4977° C (8990° F).

There are three components to each of the HID headlamps:

Fig.24 HID Ballast Module:

Ballast Module - The 12 volt Direct Current (DC) power supplied by the low beam relay is converted to Alternating Current (AC) power by the ballast module. Each lamp requires its own ballast. The ballast converts and steps up the low beam relay output to 800 volts AC, and supplies the lamp assembly via a cable connected to the igniter.

Fig.25 HID Lamp And Igniter:

Igniter - The lamp assembly contains an igniter that controls the voltage applied to the lamp electrodes. The igniter uses the voltage supplied by the ballast and momentarily steps up the voltage to 25,000 volts to start the lamp. Once ignited, it will reduce the voltage to 85 volts.

Lamp - The lamp contains electrodes and xenon gas. The lamp takes about 10-15 seconds of warm-up time to reach full operation. The light appears blue during warm-up and then turns to white.

HEADLAMP DELAY
The Headlamp Time Delay system is controlled by the Body Control Module (BCM) through the headlamp relay.

The headlamp time delay system is activated by turning the headlamps ON (high or low beam) while the engine is running, turning the ignition switch OFF, and then turning the headlamp switch OFF within 45 seconds. The system will not activate if more than 45 seconds elapse between ignition switch OFF and headlamp switch OFF The BCM will allow the headlamps to remain ON for 90 seconds before they automatically turn off. Refer to the Owner's Manual for more information.