Mr. Yanichi Yoshimoto
Deputy General Manager
Technical Administration Dep't.
Koito Manufacturing Co., Ltd.
Shizuoka Works
500,Kitawaki
Shmimzu-Shi, Shizuoka-ken
Japan

Dear Mr. Yoshimoto:

This is in reply to your letter of November 28, 1997, to the Associate Administrator for Safety Performance Standards, asking for an interpretation of the humidity test requirements of Federal Motor Vehicle Safety Standard No. 108. For your future reference, requests for interpretation should be addressed to the Chief Counsel.

After a humidity test, paragraph S7.4(h)(6) of Standard No. 108 requires the inside of a headlamp to "show no evidence of delamination or moisture, fogging or condensation visible without magnification." You ask whether moisture is nevertheless permissible if it is located in an area of the interior where it cannot affect the photometric performance of the headlamp.

The requirement is absolute: no moisture that is visible without magnification is permitted on the interior of a headlamp after the humidity test, whether or not it is located in an area related to the photometric performance of the headlamp. Thus, moisture is not permissible in the situation shown in your Case 1 (moisture on the lens area of the turn signal lamp portion of a single compartment lamp) or your Case 2 (moisture in a location outside the photometric effective area of the headlamp).

Sincerely,
John Womack
Acting Chief Counsel
d.1/8/98
ref:108