Headlamp: Description and Operation

AUTOMATIC HEADLAMP SYSTEM
On vehicles equipped with the auto headlamp feature, the BCM will control the exterior lamp operation by monitoring the mode selection switch located in the headlamp control panel. When auto headlamp mode is selected (headlamp switch in the AUTO position), the BCM will control the headlamp, parking lamp, side marker, tail and instrumentation lamps based on ambient light levels. The BCM monitors ambient light levels by using either the automatic temperature control system Sun Load Sensor, located on the top of the instrument panel cover, or by monitoring for a ON/OFF signal from the ElectroChromatic Rear View Mirror. If in auto headlamp mode, exterior lamps are on (due to darkness), and the ignition switch is cycled OFF, the BCM will enter headlamp delay mode (see Headlamp Delay Feature description).

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 (Automatic mode), the Headlamp Time Delay system will function when the ignition is switched OFF.

HEADLAMPS ON WITH WINDSHIELD 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.

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 headlamps ON position when ignition switch is ON when an open or 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.

EXTERIOR HEADLAMP CONTROL
The headlamps and parklamps are illuminated via external relays which are controlled by the body controller module (BCM). When the parklamp switch is closed to ground the BCM grounds the parklamp relay coil which provides the power to the parklamps. This same parklamp power feed is also wired back into the BCM to provide the power feed for the PWM circuit. When the headlamp switch is closed to ground the BCM grounds both the low beam and high beam headlamp relays. The position of the hi-beam select switch will determine the mode of operation.

NOTE: On Chrysler vehicle line, when the high beams are selected, both high beams and low beams will be illuminated. Dodge and Plymouth vehicle lines support only one mode of operation at a time.

HEADLAMP TIME DELAY SYSTEM
The headlamp Delay feature keeps the headlamps on for 60 seconds, giving the driver and passengers security lighting when exiting the vehicle. This feature is only available on vehicles equipped with RKE.

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 second has elapsed between ignition switch OFF and headlamp switch OFF. The BCM will allow the headlamps to remain ON for 60 seconds before they automatically turn OFF. Refer to the Owner's Manual for more information.

BATTERY PROTECTION: "PARK & HEADLAMPS"
This feature provides a battery protection scheme to avoid wearing down the battery if the customer leaves the parklamps or headlamps ON for extended periods of time with the ignition OFF. If the parklamp or headlamp switch remains in the active position for more than 3 minutes, while the ignition is OFF, the parklamps and or headlamps will be turned OFF and the input causing the lamps to be ON will be ignored. Once the 3 minute timeout has elapsed the BCM will enter sleep mode. Any change in any inputs monitored by the BCM that brings the BCM out of sleep mode, will reset the 3 minute timer (door lock/unlock), door ajar, ignition, RKE actuation, etc.).

Leaving the ignition switch in an active position (steering column unlocked, ignition on or accessory power on) will inhibit the battery protection routine from turning off the exterior lamps as described above.

HEADLAMP AIMING SYSTEMS
There two different systems for aiming the headlamp beams:
- With a Bubble Level Aiming (Town and Country)
- Without a Bubble Level Aiming (Except Town and Country)

HEADLAMP ALIGNMENT WITH BUBBLE LEVEL

Magnifying Window and Bubble Level:

The headlamps are equipped with a bubble level for up/down headlamp alignment. The bubble is centered with the vehicle on a level surface. A horizontal gauge and magnifying window is located next to the bubble level for left/right alignment. The aim on every headlamp assembly is calibrated at the headlamp manufacturer

At the vehicle assembly plant, the vertical aim is set by centering the bubble with the vehicle on a level surface. Horizontal aim is controlled by the mounting pads on each headlamp mounting panel.

When the vehicle is to be used with a heavy load, the bubble level can be used to compensate for the altered ride height.

HEADLAMP ALIGNMENT WITHOUT BUBBLE LEVEL
A properly aimed low beam headlamp, which is not equipped with a bubble level, will project the upper edge of the beam (cut-off) at the horizontal lamp centerline. There is no horizontal aiming adjustment. Horizontal aim is preset and does not require adjustment. The high beam pattern should be correct when the low beams are aligned properly.