Interpretation ID: nht68-2.4

DATE: 05/16/68

FROM: ROGER H. COMPTON -- NHTSA; SIGNATURE BY DAVID A. FAY

TO: White Trucks, Division of White Motor Corporation

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of March 20, 1968, to Mr. Lowell Z. Bridwell, requesting clarification of paragraph S3.4.3 of Federal Motor Vehicle Safety Standard No. 109.

In your referenced letter you have asked two questions as follows:

"1. While we provide as standard on all tractor models built on or after January 1, 1968, a 7-wire trailer connection and cable, is it satisfactory to furnish the 3-wire cable and connector being requested by many customer? Would we still be considered as conforming to Standard No. 103 with such a cable and contector?

2. Upon customer request, will we still be considered as conforming to the requirements of Standard No. 103 if, in addition to providing the standard double pole double throw switch which would actuate the brown circuit for the tail, clearance and certain marker lights on the trailer, we also furnish a separate switch for the black circuit on the trailer which would illeminate the remainder of the running lights, provided the trailer was wired in accordance with SAE Recommended Practice J560A."

In answer to question No. 1, either the 7-wire or 6-wire trailer connection and cable may be used on truck-tractors, provided the wiring is such that trailer tail lamps will be illuminated when the truck-tractor headlamps are illuminated. It is also to be noted that Standard No. 105 does not specify the number of wires to be used in the trailer connector and cable.

In answer to question No. 2, on trailers wired in accordance with SAE Recommended Practice J560a, a seperate switch for the black circuit on the trailer is permitted under the provisions of Standard No. 103. Again, the wiring and switching for the brown circuit must provide illumination of the tail lamps when the headlamps are illuminated.

The above answer also appear to be responsive to the questions raised in your letter of March 14, 1963.

Thank you for writing.