Continued development of light-emitting diodes (LEDs) is finally bringing the technology's advantages to practical applications for white-light versions of the long-living lamps. At the same time, renewed emphasis on a systems approach to truck lighting promises to help technicians get a handle on electrical problems, which still rank as one of the top three maintenance costs for fleets.

Red and amber marker lamps and taillights were the first commercial applications for LEDs because the technology was easily manipulated to create those colors, keeping costs down. While they cost more than similar lamps with incandescent bulbs, the long life and resistance to vibration damage more than compensated for the LEDs' higher initial price. And as they grew in popularity, volume brought prices down to the point that LED markers and stop/tail/turn lamps are now standard on many trailers and trucks.

White light, especially at relatively high brightness, has proved more difficult to generate with a solid-state diode, requiring more diodes to match the performance of incandescent or fluorescent lights. And with more diodes come higher cost, as well as packaging constraints and hotter operating temperatures, making white LEDs impractical for trucking applications. Until recently.

As is common with solid-state technology, a steady pace of technological development has significantly decreased the cost of manufacturing individual diodes, or “chips” with white-light output. Last year saw the first limited application of white LEDs as replacements for roof-mounted fluorescent fixtures inside trailers. Despite a higher initial cost, the solid-state units are especially attractive as an interior trailer light because they offer significant advantages over fluorescent or incandescent lights. They not only require less power, but can be packaged in a lower profile to cut down damage while loading, and have a much wider operating temperature range, which is especially important in refrigerated applications.

As technology continues to progress, the major manufacturers of truck lighting have also continued to expand the use of white LEDs. Not only has the cost of white LEDs continued to go down, but “brightness per chip is going up,” says Scott Robertson, business development manager for Grote Industries.

White LED work lights are one of the newer applications made practical by those advances. Grote, for example, has released a new hook-up light using its WhiteLight LEDs. The smaller form factor of the solid-state lamps allows the SuperNova LED Hook-Up Lamp to be recessed for better protection against damage. It's bright enough that one lamp can replace two incandescent units, reducing electrical load by 50W, yet providing a 250-lumen beam of light, according to Grote. The LEDs also allow users to choose from two light patterns: a focused beam for better illuminating of the nose of a trailer during hookup, or a broader flood pattern for lighting work areas in utility truck and other field-service applications.

Grote has also just released a white LED replacement for any PAR36 incandescent bulb. The Trilliant 36 “is a plug-and-play replacement anywhere you have a PAR36 now,” Robertson says. “It has a much wider, more even [light] pattern and more usable light than an incandescent, and delivers 40,000 hrs. of life, compared to 3,000 hrs. for an incandescent. It also has unique termination so it can accommodate either a U-shaped or blade terminal. That means no splicing or heat-shrink tubing to install it in an existing housing.”

Peterson Manufacturing markets its growing line of white LEDs under the Great White name and now offers solid-state work lights in a variety of forms, including swivel and fixed mounts. They use 10 diodes to produce a broad light pattern and have a 100,000-hr. life rating.

Promising “whiter and brighter” light than an incandescent lamp, Truck-Lite has released a number of white LED work lamps in a variety of sizes and shapes, including a smaller round 4-in./6-diode; a 7-in. lamp with a wide light output for construction and other field applications; and both spot and flood 4-in. lamps in rubber, chrome and steel housings.

With its strong presence in emergency vehicle lighting, Superior Signals has employed white LED technology to create a line of “vehicle scene lights” under the Illuminator Series name. Using ten diodes, the SL 10 Scene Light produces 80.6 lumens of light with a 90 deg. viewing angle from a rectangular aluminum housing.

Like the trailer lamps, the white LED work lights produce a bright “industrial” light that provides high contrast. While desirable for field work, such high-contrast lighting seems unnatural or uncomfortable in other settings, says Grote's Robertson.

The most recent advances in white LEDs have addressed that issue, developing diodes that produce a variety of white shades and allowing lamp manufacturers to now extend white LED applications into the truck cab. “Now we can get a warmer white light closer to what you have at home with white LEDs,” says Robertson. Grote is using that warmer diode in a new 4-in. interior dome light intended to replace the incandescent units typically used today, he says.

Peterson is also taking advantage of the more pleasing white light characteristics to produce a dome light scheduled to be released in the next few months, says Tim Gilbert, corporate director of heavy-duty sales. Step-well lights and reading lamps on swivel mounts are two other applications the company has developed using the newer white LEDs.

As good as all LEDs are, whether they be white, amber, red or some other color, “they're only as good as their connection,” says Gilbert. The various manufacturers have developed a number of “hard-shell” connectors that protect the more expensive LED lamps from corrosion, and now Peterson is focusing on the third and final element in a truck or trailer's lighting system, the harness, he explains.

Due to be introduced this month, Peterson's Defender System harness is fully sealed and will come with a warranty against corrosion as well as the more standard coverage for defects in material and workmanship. “Corrosion is a big deal for fleets,” says Gilbert. “Electrical issues are still in the top three in maintenance costs. We think that a system approach to light rather than a component approach will help address that issue.”