Use the table below in order to determine the harness (USA or Export) that was used in the construction of the vehicle. The harness build information is necessary in order to identify which specific wiring information to use.

The exterior lighting system includes the following components:

The headlamp bulbs on this vehicle contain halogen gas.

Caution: Halogen bulbs contain gas under pressure. Handling a bulb improperly could cause it to shatter into flying glass fragments. To help avoid personal injury:

Backup Lamps

The backup lamps are designed to operate only with the ignition on. Placing the shift lever in reverse closes the circuit that illuminates the backup lamps. This is accomplished through the neutral safety backup switch. The switch is located on the transaxle.

On the DeVille and Eldorado, the backup lamps are located on either side of the license plate pocket.

High Mounted Stoplamp

The high mounted stoplamp is located in the center of the rear window shelf on the DeVille and Eldorado. It operates simultaneously with the rear stop lamps and provides increased visibility during vehicle braking.

Daytime Running Lamps

The DeVille utilizes a slightly different daytime running lamp (DRL) system than that of the Eldorado. The DeVille DRL system requires the use of a DRL resistor. The system also illuminates the low beam headlamps at a reduced brightness. The Eldorado DRL system does not use a resistor and illuminates the high beam headlamps at a reduced brightness.

Regular operation of the headlamps will disengage the DRL system. If the parking lamps are turned on, the DRL still operates.

Front and Rear Side Marker Lamps (Eldorado)

The Eldorado front and rear side marker lamps are located in the bumper fascia. The front lamp lens is amber colored. The rear lamp lens is red. Both the front lamp and the rear lamp are serviced from the backside of the bumper fascia. Service does not require removal of the bumper. The side marker lamps illuminate whenever the park lamps are on. The lamps contain reflectors for increased nighttime driving safety.

Front Park/Cornering Lamps (Eldorado)

The Eldorado park/cornering lamp is mounted outboard from the headlamp. The cornering lamp is lit during turn signal operation and illuminates the peripheral area of the turn. The lamp is clear in color.

Front Park/Turn Signal Lamps (DeVille)

On the DeVille, the front park/turn signal lamp is an integral part of the headlamp.

Front Side Marker/Cornering Lamps (DeVille)

The DeVille front side marker/cornering lamp is mounted outboard from the headlamp. The side marker lamps illuminate whenever the park lamps are on. The lamps contain reflectors for increased nighttime driving safety. The cornering lamp is lit during turn signal operation in order to illuminate the peripheral area of the turn. The side marker lamps are amber in color. The cornering lamps are clear.

Fog Lamps (DeVille and YP8)

The fog lamps light when the parking lamps or the low beam headlamps are on and the fog lamp switch is on. When these conditions are met, the fog lamp circuits contained within the body wiring harness apply voltage to the fog lamps.

Headlamps

The headlamps consist of 2 interchangeable, double filament bulbs which provide both high and low beams. The inner bulb in the headlamp is the high beam. The outer bulb is the low beam.

Upon turning on the headlamps, activating the HI/LO switch will cause the high and low beam relays to toggle to the high beam state and latch. The high and low beam relays will only change states if the headlamps are turned off or the HI/LO switch is activated again. If the headlamps are off, activation of the HI/LO switch controls the flash-to-pass feature.

The flash-to-pass system requires the high beam headlamps to be activated for the duration of activation of the HI/LO beam switch if the headlamps are off. When the HI/LO beam switch closes, the headlamps come on directly in the high beam state without going through the low beam state. The ignition must be on for the flash-to-pass to operate.

Wiper Activated Headlamps

The wiper activated headlamps function allows the headlamps and the park lamps to be activated by the windshield wiper switch. If the twilight sentinel is on and the wiper switch is activated, the headlamps and park lamps come on after 23 seconds of wiper operation. If either the twilight sentinel or the wiper switch are deactivated, the headlamps and the park lamps turn off.

Tail Lamps

On DeVille, the tail/stop/turn signal functions are performed by one lamp. It consists of a red lens, 2 tail/stop/turn signal bulbs, and a fiber optic connector for the rear lamp monitor system.

On the Eldorado, the tail/stop/ turn signal functions are performed by one lamp. It consists of a red lens, a tail lamp bulb, and 2 tail/stop/turn signal bulbs.

Rear Side Marker Lamps (DeVille)

The DeVille rear side marker lamps are mounted to the rear quarter panel and retained by 2 nuts accessible from inside the rear compartment. The quarter panel body side molding must be removed before servicing the lamp. Refer to General Body Service. The rear side marker lamps illuminate whenever the park lamps are on. The lamps contain reflectors for increased nighttime driving safety. The lamps are red in color.

The headlamp switch controls power to the exterior lighting. The switch is located in the instrument panel, to the left of the instrument panel cluster. There is one switch to illuminate only the park lamps, to illuminate the headlamps and park lamps, and to shut all exterior lighting off. Automatic on/off control of the exterior lighting is available with the twilight sentinel system. The twilight sentinel switch is located to the right of the headlamp switch, on the left switch pod.

An audible alarm is wired into the headlamp control system to prevent the driver from leaving the vehicle with the lights on. Refer to Audible Warnings in Electrical Diagnosis for circuit details on the audible alarm system.

Switching between high beams and low beams is accomplished using the column-mounted dimmer switch. The dimmer switch is operated by pulling back gently on the turn signal lever.

The dimmer switch for interior lights is part of the headlamp switch.

The dimming of vacuum fluorescent displays is performed if the park lamps are on and the twilight photocell indicates darkness. The dimming of incandescent lamps is performed any time the park lamps are on, independent of the photocell status.

Dimming of the interior lighting systems is as follows:

The illuminated entry system provides the driver with a timed illumination of the courtesy lamps when entering the vehicle. When either door handle switch is activated (the switch is grounded), the courtesy lamp relay is activated for 20 seconds. Turning the ignition switch on during the timeout period terminates illuminated entry.

The turn signal lever controls the operation of the front and rear turn signal lamps and the cornering lamps.

The hazard warning flasher switch, located on the right side of the steering column, activates the hazard warning flashers. Both of the turn signals flash when the hazard lamps are activated.

The twilight sentinel is a convenience system that controls the operation of the exterior lamps in response to the level of the ambient light. The system provides a light sensitive on/off control of the lamps which would otherwise be done manually with the lamp switch. The system also keeps the lamps on for a pre-selected period of time after the ignition is turned off to improve night visibility when leaving the vehicle. The lamps will be turned off automatically after the preselected time period elapses (from a few seconds to 3 minutes).

A light sensitive photocell is mounted with the light sensitive surface up under the center front defroster grille so that the sensor has an unobstructed view of the ambient light through the windshield. The driver control switch is located on the left switch pod.

System Operation

The twilight sentinel system operates automatically whenever the ignition switch is on, the headlamp switch is off, and driver control is turned on (any position other than off). The system will turn on the lamps when the daylight is reduced to a point at which illumination is necessary. As daylight increases in the morning and illumination is no longer necessary, the system will turn the lights off.

A time delay feature reduces the frequency of undesired switching of the lamps while passing under viaducts, trees, bright lights, etc. The time delay is normally 8 - 20 seconds, and cannot be altered or adjusted. The potentiometer controls only the time delay period during which lamps will remain on after the ignition is turned off. The driver may preselect any desired time delay, from a few seconds to a maximum of 180 seconds.

Slide the potentiometer to the OFF position when the lamps are undesirable, such as driving in tunnels that require lamps off, or if the twilight sentinel malfunctions. This disables the twilight sentinel. The lamps will now operate only with the regular lamp switch. If the lights are desirable during daylight hours, the driver can use either of 2 methods to turn the lights on: