The Fleet Business Authority
Issue link: http://heavydutytrucking.epubxp.com/i/221397
Trailers Included in the system are wiring jacketing, wiring gauge, terminals, connectors, processors, lamps and installation. The RP also included some installation best practices, which can provide guidance to help improve the performance of the system. Revised RP-704C includes a wiring schematic for a typical trailer. Note that either one or two lamps may be used at each of the trailer's corners. A single lamp can be in the corner radius, or on the side within 6 inches of the nose. A side-mounted lamp must be PC rated, meaning its light is visible from ahead and behind. This LED lamp's lens spreads light across 180 degrees of view, and its four diodes ensure sufficient candlepower throughout that wide angle to meet or exceed the federal regulations. The lamp is therefore "PC rated," with the C meaning Combination clearance and sidemarker, and it can be mounted on the trailer's side, though within 6 inches of its nose. (P for Parking, is from an old , industry classification that has been retained.) This trailer's front corner looks like it's been battered by tree branches or something worse. But its clearance lamp has survived because it's mounted to the side – permissible under federal rules – and within the top sill's channel. 64 HDT • DECEMBER 2013 2 LED diodes can still fail Lamps using light-emitting-diodes have become common on trailers and power units since being introduced by Grote Industries more than two decades ago. LEDs use about onetenth the current of incandescent bulbs and last 10 times as long. Most LED lamps have multiple light-emitting diodes, so if one or a group of diodes fails, the lamp still works. But is there a percentage of burned-out diodes that defines lamp failure and leads to a citation? ficer's discretion." Vehicle Committee members deliberated the question at a meeting in 2004 but couldn't come up with an answer. The inspection questions related to LED lamp failure involve: • When should a failing LED lamp be replaced? • How many individual LEDs should remain 'on' for the lamp to be acceptable? • Is there a failure 'rule' for each type and brand of LED lamp? The committee asked the National Highway Traffic Safety Administration and the Federal Motor Carrier Safety Administration for guidance, but they couldn't provide any. Neither could manufacturers, though one told the CVSA committee that it issued special cards that customers could use to measure light output. Lacking enlightenment from those sources, committee members closed the matter. In Canada, National Safety Code Standard 11 Part B states, in part, that a lamp should be "rejected" if "Ultimately, if it's still visible, it's still lighting. And ultimately it comes down to the officer's discretion." – Will Schaefer, CVSA Not in the United States, according to Will Schaefer, director of vehicle programs at the Commercial Vehicle Safety Alliance. CVSA members are state, provincial and local enforcement officials in the U.S., Canada and Mexico. Together they set standards regarding equipment – but there is none for LEDs. "We have analyzed it extensively in our Vehicle Committee," he says. "When one diode goes out, the rest may get brighter. In the end, we do not have a good way of knowing that if two out of three, or three out of seven, or four out of 15 are not lighting, would that cause a total reduction of enough light to constitute a failure? Ultimately, if it's still visible, it's still lighting. And ultimately it comes down to the of- "25% or more of LEDs of any one lamp assembly are non-functional." However, Alberta officials, in alerting CVSA to this standard, note that "a NHTSA study indicated 80% of the population cannot tell when lights have lost 25% of their intensity." Like all lamps, an LED type must meet light-output standards expressed in Federal Motor Vehicle Safety Standard 108, which says a lamp's output must be visible from 500 feet. If some light is visible at that distance, it might or might not be judged OK by an inspector. ■ Read more on trailers each week from Senior Editor Tom Berg in his Trailer Talk blog at www.truckinginfo.com/ trailer-talk www.truckinginfo.com www truckinginfo com