Interpretation ID: nht71-3.45

DATE: 07/21/71

FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA

TO: Rueck and Company

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of July 7, 1971, to the National Highway Safety Bureau (now the National Highway Traffic Safety Administration) concerning the requirements for sealed beam headlamp units.

The answers to your specific questions are as follows:

1. Sealed beam units must meet the photometric specifications in SAE J579 at the design voltage at or below the maximum amperes specified in SAE J573.

2. Tolerances are as follows:

Electrical power - the maximum electrical power is the product, in watts, of the design voltage multiplied by the maximum amperes at design volts. There is no specified minimum electrical power.

Maximum amperes - There is no tolerance. Maximum amperes is the maximum specified in SAE J573.

Design watts - There is no tolerance. There is, however, a tolerance on the actual watts or electrical power as described above.

3.4.4. The filament types and positions are illustrative of current practice only. Any type or position may be used to meet the specification of J579 and J573.

5. All glass sealed beam units are not mandatory. There are no restriction in Federal Motor Vehicle Safety Standard No. 108 or the SAE Standards on the number of pieces or the materials which are used to complete the assembled sealed beam unit as long as the specifications, including those in SAE J571, are met. Caution should be used, however, to ensure that a good and durable seal is obtained between the metal back, if used, and the other parts to optimize the useful service life of the sealed beam unit.