Interpretation ID: 7113
Manager, Information Services
Ichikoh America, Inc.
Suite 220
3025 Boardwalk Drive
Ann Arbor, MI 48108-1777
Dear Mr. Aihara:
This responds to your letter of March 16, 1992, requesting an interpretation of the applicability of the moisture prohibition of S7.4(i)(6) of Federal Motor Vehicle Safety Standard No. 108.
Initially, we would like to call your attention to the fact that S7.4(i)(6), which you quoted in its entirety, was amended on March 11, 1991, to delete the requirement that a headlamp meet the photometric requirements after a humidity test. S7.4(i)(6) now states in pertinent part that, after a humidity test conducted in accordance with S8.7, "the inside of the headlamp shall show no evidence of delamination or moisture, fogging or condensation visible without magnification."
You have attached a drawing of a vented headlamp with an onboard aiming system. The headlamp is available with two different types of bubble indicators. Your first question is: "After the humidity test, both types . . . show the fogging in the location as shown in attached sketches. But, this fogging is gone at normal temperature. * * * Is such fogging acceptable after the humidity test?" Your second question is whether "'the inside of the housing' means the lens and reflector portions" or "the entire inside portion of headlamps?"
The humidity test was adopted for replaceable bulb headlamps in l983. Allowing humidity or water in headlamps causes slow degradation of the reflector over the long term. The presence of humidity results in spots on the reflector and lens, and eventual photometric failure. The humidity test is designed to assure that the vents in vented headlamps eliminate moisture in the headlamp when exposed to air flow with the headlamps off, thus assuring adequate performance in long term use. The provision for onboard headlamp aiming devices was not adopted until 1989, and, with respect to replaceable bulb headlamps, did not specify that they be located within the headlamp. From the foregoing, it is evident that the humidity test for replaceable bulb headlamps was not adopted to address a problem inherent in the exposure of onboard aiming devices to moisture. These devices were not in use at the time the humidity test was added to Standard No. 108, and they do not contribute directly to the photometric performance of the headlamp.
From the diagram you enclosed, the aiming device appears located behind the reflector. It is not possible to determine from your letter whether moisture forms on the exterior or the interior of the aiming device. Although S7.4(i)(6) prohibits moisture "inside the headlamp" and the aiming device is located inside the headlamp, we would not read the prohibition as extending to the aiming device if the moisture occurs inside that device.
Even if the moisture occurs on the exterior of the aiming device, it does not affect the photometric properties of the headlamp. The agency does not wish to impose inadvertent design restrictions that are not directed towards safety, and therefore regards any moisture that may occur on the exterior of the aiming device as outside the prohibition of S7.4(i)(6). This interpretation, however, is limited to the specific design that you have presented.
Sincerely,
Paul Jackson Rice Chief Counsel
ref:108 d:5/6/92