Interpretation ID: 7857

Mr. T. Kouchi Director & General Manager Automotive Equipment Development & Administration Dept. Stanley Electric Co. Ltd. 2-9-13, Nakameguro-ku, Meguro-ku Tokyo 153, Japan

Dear Mr. Kouchi:

This responds to your letter of October 8, 1992, with respect to photometric test methods for a center high-mounted stop lamp using light emitting diodes (LEDs) as light sources.

Your letter presents certain procedures and asks for associated revisions in Federal Motor Vehicle Safety Standard No. 108. After review, we have come to the conclusion that your method of proposed testing is allowable under Standard No. 108, but more stringent than what the standard requires.

In the section of your letter called "BACKGROUND", you state that you usually follow the technical guidance of SAE J1889 as a standard practice for LED lighting devices. There is no requirement in Standard No. 108 or in any of the SAE standards incorporated by reference in Standard No. 108 that requires you to follow the test methodology of J1889. Thus, when you say that you "must always allow a margin of the same percentage when designing initial light output of the lamp, which necessitates increase in the number of LEDs used, lamp size, product cost, and, therefore, user's expense", you are placing a burden upon yourself that does exist under J1889, but one which is not necessary for designing for compliance with Standard No. 108.

You have proposed a solution for the problem you have created by following J1889, and you provide three specific reasons in support. The third reason is based upon your interpretation of SAE J575's warpage test, under which you test operating cycles of 5 minutes on and 5 minutes off. However, you reference a version of J575 which does not apply to center high-mounted stop lamps. Paragraph S6.1 of Standard No. 108 specifies that J575e, August 1970, applies to high-mounted stop lamps designed to conform to SAE Recommended Practice J186a. SAE J575, August 1970, simply specifies that the device is to be operated in the test in the same manner as it will be operated in service, far different than the cycle method you employ.

Thus, you have requested that we revise Standard No. 108 by adding a new provision that center high-mounted stop lamps shall be energized for a minimum of 5 minutes before measurement of photometric minima. We note that nothing prohibits you from testing in such a manner, but we believe that an amendment of this nature is not required because the present allowable method of testing does not call for it.

You have asked for our comments on four steps of photometric measurement, and our permission to follow them. There is no reason you may not follow them, if you wish, but they are unnecessary to design for compliance under Standard No. 108.

I hope that this is responsive to your questions.

Sincerely,

Paul Jackson Rice Chief Counsel ref:108 d:12/1/92