Interpretation ID: nht79-1.41

DATE: 08/09/79

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Porshe

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of May 25, 1979, requesting clarification of Federal Motor Vehicle Safety Standard No. 101-80, Controls and Displays. You asked whether the rear window defogger switch, which emits a dim light for control location and a brighter light upon activation, is considered a control or a telltale.

Although the switch might be regarded as a control, telltale, or both, it is regulated as a control insofar as its illumination is concerned. Therefore, its illumination must be continuously variable as specified in S5.3.3 of the standard.

S5.3.3 provides that

Each passenger car . . . manufactured with any control listed in S5.1 or in column 1 of Table 1, and each passenger car . . . with any display listed in S5.1 or in column 1 of Table 2, shall meet the requirements of this standard for the location, identification, and illumination of such control or display.

The rear window defrosting and defogging system appears in the control list of S5.1 and in Table 1, but not in the display list of S5.1 or in Table 2. Therefore, the control illumination requirements of S5 apply to the defogging switch and the display illumination requirements do not.

If you have any further questions, please do not hesitate to write.

SINCERELY,

UNITED STATES COMPLIANCE OFFICE

NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION Office of the Chief Counsel

May 25, 1979

Subject: PART 571, FMVSS 101-80, Docket 1-18, Notice 13 Control Location, Identification and Illumination

Dear Sirs:

In Table 1 of the above docket, the rear window defrosting and defogging system control shall be illuminated.

S 5.3.3 reads: "Light intensities for controls etc. and their identification shall be continously variable. . ."

In the same paragraph it reads: "The light intensity of each telltale shall not be variable and shall be such that, when activated, that telltale and its identification are visible to the driver under all daytime and nighttime conditions."

In one of our cars, the Porsche 928, the dashboard illumination and a dim light inside the rear window defogger switch are activated when the ignition is turned on. The dim light within the defogger switch is meant to help to locate this control. Upon activation of this switch the light intensity of the defogger switch is increased to show that the rear window defogger switch is in the "on" position. Both light intensities, dim to locate the control, and brighter for activation, are not variable.

Please clarify if w should consider the light in the rear window defogger switch a "telltale" or a "Control" and if we are in compliance with the 2 different light intensities.

We enclose 2 pictures from the owner's manual to show the location and activation of the switch.

Thank you in advance for your clarification.

Gerhard C. Waizmann

Enclosures omitted.