Lighting Systems: Illuminating the repair process

Lighting Systems

Often thought of as just another part to change out, modern lighting systems are a major safety item requiring proper installation and aiming.Lights serve two purposes on vehicles: The first is to illuminate the road for the driver to see where he or she is going. The second is to make sure other drivers can see your vehicle. Today’s cars and trucks are required to have several lights, including tail lights; markers; stop and turn signals; a third brake light located high and centered; side marker lights in the front and rear; and marker and turn signal lights at the front. Headlights must alert other drivers without shining in their eyes. This is why all vehicles have low beams, which have a sharply defined pattern of light. High beams have more of a flood pattern. History
Development of lighting systems started with slow-moving carriages, which needed little more than a lantern, taken right off of their horse-drawn predecessors. Carbide and, later, incandescent lamps followed. In the 1920s, the “Duplo” lamp was developed, featuring two filaments. Thirty years later the “Duplo-d” lamp was introduced. This lamp had an asymmetrical light beam, allowing a low beam with a cut-off pattern. This was an important safety development because the driver needed to see the road and be seen by other drivers, but avoid blinding the drivers of oncoming cars. It was the mid-1960s that halogen bulbs were first used in Europe. Halogen lamps produce about twice the amount of light as incandescent sealed beams. Until 1975, all U.S. headlights had to be round, non-halogen, U.S. Department of Transportation (DOT)-approved sealed beam units. These were parabolic reflectors containing a glowing incandescent filament with a glass lens used to attenuate the beam. In 1985, the U.S. DOT adopted its current lighting standard, which is based on European regulations. It allows for halogen lamps and non-standard shapes. Ellipsoidal, or projector, designs and free-form reflector designs are almost twice as efficient at using a bulb’s light to illuminate the road. The clear lens allows the vehicle’s designer to shape the outside of the lamp module to fit its bodylines. Today, the leading edge of lighting is high-intensity discharge (HID). These lamps use xenon gas with a small amount of mercury and two electrodes housed in a small bulb. They have much in common with fluorescent bulbs, using electrical energy to vaporize the mercury, which increases the pressure in the bulb. For this reason, these may be referred to as high-pressure lighting systems. The xenon gas glows at very high temperatures, producing light. These systems use much less energy after they are started. A 55-watt halogen lamp draws 10 to 15 amps continuously, producing 1,250 lumens of light. A 35-watt HID system uses 20 amps to start, but then only requires 4 amps, producing 3,200 lumens of light. These lamps are more expensive and are not yet common except on luxury cars. In Europe, they must be equipped with automatic leveling systems to maintain proper vertical aim under differing load conditions. This is not a requirement in the United States.Low-pressure lights, which use different gases, such as neon, are being developed for marker and brake lights. LED light sources are also used for marker lights. One advantage of low-pressure and LED lighting systems is that they should last at least the life of the car and never need replacement under normal driving conditions. Another observable advantage for brake lights is faster illumination than incandescent bulbs. Conventional filament brake lights switch on in about 200 milliseconds, but a low-pressure, gas-discharge light will reach full intensity in less than a millisecond. In road and simulator tests, this has results in significantly reduced stopping distance for vehicles following other drivers, according to research conducted by Philips and Mercedes. One future development is fiber optics. Bundles of very small glass fibers are used to direct light where it is needed. Visible light is absorbed by these fibers, so a very powerful light source must be used. With high-pressure systems, there is enough light energy to provide all the lighting needs of a single vehicle from one source. A centrally located bulb could be used to power all marker, interior and headlights. The systems have been demonstrated in show cars and may show up in production models soon.

Viewed from the front, all that is seen of this fog light and marker lamp is the lens and reflectors. From behind, the housing is seen to extend behind the bumper cover. Discovering damage to this part of the lamps may be difficult during initial inspections.Replacement and repair issues
Of course, lighting systems are some of the first parts to be damaged during collisions. Marker and signal lamps are located near the four corners of the vehicle, often mounted in the bumper systems or exterior body panels. Replacing these items is routine for most technicians, although the plastic housings can be overlooked at the time of the initial estimating process. During vehicle teardown, make sure to note all cracked components. Headlights are another matter. The old days of sealed beams have given way to molded plastic, multifunction units, which are usually replaced as modules. For many technicians, these are a welcome development. Four headlight sealed beam systems with mounting panels, retaining rings, adjusting screws and springs were often like a puzzle without all the pieces. A one-piece unit, held in place with a few fasteners is much less work. Perhaps more critical are the mounting surfaces on which the headlight module is secured. With limited aiming on some systems, core support and any mounting brackets must be precisely located during structural repairs for the headlight module to fit properly.Plastic repair techniques are seldom used with marker and signal lights or headlight modules. Mounting tabs can be reattached, and small cracks can be repaired. Usually if a housing is cracked, the reflector is also damaged, making repairs impossible. New materials using a powder and liquid to make clear, amber and red lens repairs are available to fix those small holes caused by stones. These repairs are not invisible, so they may not be acceptable cosmetically. But they offer an alternative for some situations and temporary repairs.

Park the car on a level floor facing a wall or screen 25 ft. away. Measure the distance from the ground to the geometric center of the headlights. On some lights, there is a little molded mark to indicate this center. Transfer this measurement to the wall. Measure the distance between the lights. Transfer this and the centerline of the vehicle to the wall. Now mark a line 2.1 in. below the horizontal you marked on the wall. Turn on the lights and set the low beams to intersect the lower line and the vertical lines where the angle in the beam starts to slope upward. W ith some lights, the pattern of light on the wall is hard to judge precisely. An overlooked repair technique is sanding and polishing the lenses. Often only minor scratches are present. Many of the plastics in use today are easily sanded and polished. The materials you need are located in the refinish department. Just as when sanding clearcoat, start with the finest paper that will eliminate the scratch, work up to 2,000-grit paper and machine polish. This will take out those minor scuffs and scratches. It will not fix hazed or yellowed lenses on older headlights, although it may improve the appearance.Wiring is often cut or stretches during a collision. Inspection of all wiring near the damage should allow timely repair or replacement. With HID systems there may be power units mounted near the headlights. All wiring repair should be done using approved crimp splices with heat shrink ends. Aiming
Aiming headlights is a critical part of vehicle repair. This is probably one of the most overlooked details in the collision repair industry. Too few shops have the proper equipment to properly aim headlights. There are several choices, starting with a manual process involving taking measurements and aiming the light against a wall or screen. During this process, park the car on a level floor facing a wall or screen 25 ft. away. Measure the vertical distance to the geometric center of the headlights. This is the hard part—what is the geometric center? On some lights, there is a little molded mark to indicate this center. On others, it will be necessary to look into the lens and judge where the center of the bulb is. Transfer this measurement to the wall. Measure the distance between the lights. Transfer this and the centerline of the vehicle to the wall. Now mark a line 2.1 in. below the horizontal you marked on the wall. Turn on the lights and set the low beams to intersect the lower line and the vertical lines where the angle in the beam starts to slope upward. The obvious problem with this system is all the time it takes. Not to mention the difficulty of accurately making all of those measurements. Also, with some lights, the pattern of light on the wall is hard to judge precisely. An alternative is a headlight-aiming machine. These come in simple and affordable optical units, as well as sophisticated electronic units that provide a printout for the customer file. Aiming is relatively quick and easy with these systems. The devices are placed in front of the vehicle and centered on the headlights, usually with a visual aid built into the system. Then a pattern is observed and adjustments made until it lines up. It’s easy and accurate. Conclusion
Beyond the normal damage to components as part of a collision, include a lighting system check in your estimating and final quality control procedure. Lighting system components, particularly bulbs, may become damage away from the point of impact due to the physical forces involved in the collision. With lighting system basics under your belt, coupled with a thorough system check, you can assure the safety and customer satisfaction of your lighting system repairs.