At what point will malfunctioning Light Emitting Diode (LED) elements in a lamp render it ineffective, even though it still produces reduced light?
This was discussed at the Commercial Vehicle Safety Alliance (CVSA) April 2000 meeting. Minutes of the CVSA meeting plus a paper on inspecting LED lamps increase understanding of LED technology and the difficulty in determining how many elements must be out before the lamp is considered defective.
CVSA Minutes
LED Lamp Segments Not Working (00-014-VEH)
During the April 2000 meeting in Tampa, FL Mr. Vince Babich raised a concern relating to light emitting diode (LED) lamps. At some point malfunctioning LED elements in a lamp will result in it becoming ineffective even though it still produces reduced light. The North American Uniform Out-Of-Service (OOS) Criteria does not address a partially operating condition.
Secretary Strawhorn contacted the LED lamp manufacturers, National Highway Traffic Safety Administration (NHTSA) and The Maintenance Council of the American Trucking Association (ATA) in an effort to determine how many "blanks" can exist in an LED lamp before it should be considered inoperative for OOS purposes. There is no universal answer to the question. Mr. Strawhorn wrote up what he learned about LED lamps and that paper can now be considered final as it has been reviewed by the major LED suppliers and the Department of Transportation (DOT). Copies were handed out and are Attachment B to these minutes. Unfortunately there is no universally acceptable way for inspectors to declare a partially operating LED lamp ineffective.
Given there is nothing to use to judge how many elements must be out before the lamp is defective, there were deliberations about how to handle LED lamps with malfunctioning elements. The discussions led to a conclusion that such lamps should be viewed from a distance of 500 feet and considered ineffective if they do not appear to be operating.
Another obstacle to inspecting LEDs is that they are very directional. This means that if they are observed at an angle other than that at which they are required to shine, they may be functioning properly and appear to be off. It is important to check LEDs from several angles before concluding that they are not working.