By Larry Carley
Technical Editor

Nothing lasts forever and headlights and other bulbs are no exception. After 1,000 or more hours of operation, the light-emitting tungsten filament eventually burns out, causing the lamp to fail. Vibration is another factor that can shorten the life of any bulb and headlights are always vulnerable to stones and debris kicked up by other vehicles, not to mention collision damage.

The loss of a headlight makes nighttime driving hazardous and may even attract the unwanted attention of the local police. A burned-out taillight, stoplight or turn indicator lamp creates a hazard for other motorists because these lamps signal a vehicle’s directional intentions to other drivers. Bulbs that provide illumination for instrumentation are also important because they allow the driver to monitor the speedometer and other gauges. Even something as simple as a failed trunk light or dome light can create an inconvenience when operating a vehicle after dark. So your job is to help customers see the light when they need a replacement lamp or bulb.

Years ago, all headlights were sealed beams. So if a customer needs a replacement headlight for a 1980s vintage or older vehicle, there are only a few basic sizes of round and rectangular beams: Those for two headlight applications (6014 round hi/low sealed beam and 6052 rectangular hi/low beam) and those for four headlight systems (4000 round low beam, 4001 round hi beam, 4652 rectangular low beam and 4651 rectangular high beam).

Most of these older-style sealed beams were originally standard incandescent lamps. In 1978, the federal government revised its headlight regulations to allow the use of “halogen” sealed beams. Halogen lamps are brighter and last longer than regular lamps because the bulbs contain a small amount of bromine gas (one of five elements in the halogen chemical family). The bromine gas allows the use of a smaller, hotter tungsten filament because bromine redeposits the microscopic particles of tungsten that boil off the filament back onto the wire. This extends the life of the bulb and prevents the glass from darkening as the bulb ages.

Halogen lamps are a good upgrade for these older sealed beam applications because halogen lamps produce more light with the same or less current. Halogen sealed beams have an “H” prefix on their part numbers and are available in various sizes for round, rectangular and low-profile rectangular headlights.

How much brighter are they? A conventional incandescent bulb generates 16 to 18 lumens of light per watt, compared to 20 to 22 or more lumens per watt for a standard halogen bulb (some high output halogen bulbs produce as much as 28 to 33 lumens per watt!). The higher output of a halogen headlight throws more light on the road to improve nighttime visibility and extend the driver’s visual range. The light is also whiter than a regular incandescent bulb, which improves visibility too.

In 1983, the feds approved the use of “composite” headlight assemblies with plastic covers and replaceable bulbs. This gave the vehicle manufacturers more design freedom, reduced the lighting system’s vulnerability to stone damage and made it easier in many instances to replace a headlight. But it also spawned the introduction of a growing number of new halogen bulb configurations.

Some of the more popular replacement halogen bulbs include 9004, 9007, 9008 and H4 for two headlight systems, 9006, H1, H7 and H11 for low beam quad headlight applications, and 9005 and H9 for the high beam on quad lamp systems. For fog and auxiliary lamps, other popular halogen replacement lamp sizes include 9040, 9045, 9055, 9140, 9145, 9155, H3 and H8.

XENON: A STEP UP
In the late 1990s, two new types of “xenon” headlights were introduced. One type is the “High Intensity Discharge” or HID lighting system that uses a special high voltage bulb that contains no filament. Inside the HID bulb are two electrodes separated by a gap and a mixture of xenon gas, mercury and halide salts. A ballast unit steps up the base voltage supplied to the HID lamp to create an electrical arc between the electrodes. This produces a “plasma discharge” inside the bulb that gives off a very bright, bluish-colored light for better night vision and range.

HID lighting systems are much more efficient than standard halogen headlights, producing about 75 lumens per watt. And because an HID bulb has no filament to burn out, they last three to five times longer than a standard halogen bulb. But the required ballast electronics also makes HID lighting systems very expensive so they are used primarily on high end luxury cars and SUVs. HID replacement bulbs include D1S, D1R, D2s and D2R. Aftermarket HID lighting kits are also available to upgrade a vehicle’s lighting system.

A more affordable upgrade alternative are blue xenon headlights that can replace standard halogen bulbs. The blue bulbs have a tungsten filament like a standard halogen bulb, but also contain xenon gas that allows the bulb to burn hotter and brighter (up to 30 percent more light depending on the application). The special coating also gives the light a bluish cast that appears similar to that of a real HID lighting system.

FINDING THE RIGHT ONE
With all types of lighting applications, finding the right replacement bulb is essential. Small bulbs, in particular, can be difficult to match. Always refer to a lighting catalog or database for the vehicle application. Comparing bulbs and referring to the number on the old bulb is also a good idea, but keep in mind that the old bulb may not be the correct one for the application if it has been replaced before (maybe that’s why it burned out!). Two bulbs that appear to be the same may have different wattage and resistance ratings. Using the wrong bulb may cause premature bulb failure, circuit overloads or other problems.

On some newer vehicles, “light out” modules are used to sense failed bulbs and alert the driver when a lamp fails. If a replacement bulb does not have the same resistance and wattage rating as the original, it can sometimes cause the module to illuminate the “light out” warning lamp even though the bulb is working.

With halogen and xenon headlights, the lamp receptacle in the headlight housing and wiring connectors are configured differently to eliminate the risk of installing the wrong replacement bulb. Customers should be warned, though, not to touch the bulb itself because fingerprints can cause a high-temperature bulb to fail prematurely.