Interpretation ID: nht69-2.34

DATE: 10/09/69

FROM: AUTHOR UNAVAILABLE; R. A. Diaz for R. Brenner; NHTSA

TO: Department of California Highway Patrol

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of September 10, 1969, concerning lamp bulbs to be used in photometric tests.

In answer to your first question, photometric testing of lamps using 1034 and 1157 bulbs should be conducted with the minor filament operating at four mean spherical candlepower to determine conformance to SAE J573b. Bulbs utilizing three candlepower minor filaments would not be in conformance with SAE J573b; however, as provided by the enclosed interpretation issued August 12, 1968, on bulbs and bulb sockets, such bulbs may be used in lamp assemblies conforming to Federal Motor Vehicle Safety Standard No. 108. In accordance with the interpretation, such bulbs should be treated as special bulbs and should be tested at the three candlepower rating.

In answer to your second question, if photometric tests are conducted with a bulb operated at either three or four mean spherical candlepower ratings, it is not acceptable to interpolate (or extrapolate) the data to determine acceptability of the lamp in the other bulb rating.