Interpretation ID: 1984-2.36

TYPE: INTERPRETATION-NHTSA

DATE: 07/24/84

FROM: AUTHOR UNAVAILABLE; Frank Berndt; NHTSA

TO: Porsche -- Hd. Herrn Mayer/ESV

TITLE: FMVSS INTERPRETATION

TEXT:

Dr.Ing.h.c.F.Porsche AG z. Hd. Herrn Mayer/ESV Postfach 11 40 7251 Weissach WEST GERMANY

Dear Mr. Mayer:

This responds to your letter of June 19, 1984, asking about Standard No. 105, Hydraulic Brake Systems. You asked whether it is permissible to limit activation of the brake system indicator lamp for purposes of checking the indicator lamp function to six seconds.

The answer to your question is yes. I have enclosed a copy of a letter addressed to Fiat, dated February 7, 1975, which discusses this issue.

Sincerely,

Frank Berndt Chief Counsel

Enclosure

Mr. Ralph Hitchcock -- NHTSA

ESVG/My-re Weissach, June 19, 1984

Request for Clarification

Ref: FMVSS 571.105, S 5.3

Dear Mr. Hitchcock:

The above-mentioned FMVSS also requires the possibility for the driver of a motor vehicle to check the brake system indicator lamp (S.5.3.2) before he or she starts the car.

The two alternatives mentioned are:

All indicator lamps shall be activated as a check of lamp function either

a) when the ignition (start) switch is turned to the "on" (run) position when the engine is not running, or

b) when the ignition (start) switch is in a position between "on" (run) and "start" that is designated by the manufacturer as a check position.

Point S 5.3.3 also requests:

Each indicator lamp activated due to a condition specified in S 5.3.1 shall remain activated as long as the condition exists, whenever the ignition (start) switch is in the "on" (run) position, whether or not the engine is running.

Assuming there is a defect in the brake system, as specified in S 5.3.1 a), b) or c), and the driver turns the ignition switch to the "on" position and the engine is not running, there will be no definite indication before starting the engine that there is a defect, since the indicator lamp is also activated to control the function of the lamp itself.

This means, the indicator lamp can be activated for two reasons, but without making the distinction between the dangerous situation as specified in S 5.3.3 and the more harmless situation specified in S 5.3.2.

We would now like to eliminate this uncertainty by limiting the activation of the lamp (specified in S 5.3.2) to 6 seconds, i.e. if the brake system is working properly the indicator lamp will dim after 6 seconds while it will remain activated if there is a malfunction in the brake system.

This improvement could be achieved by combining the brake system indicator lamps with the time-limit relay of the 'Fasten Seat Belts'-lamp which is activated for 4 - 8 seconds after the ignition switch is moved to the "on" position or the "start" position (S 7.3 FMVSS 208).

We would now like to know if this method of controlling the function of the brake indicator lamp complies with the requirements in S 5.3.2 of FMVSS 105?

An early favorable answer would be greatly appreciated as we intend to use this method in a 1985-model in connection with the introduction of a modified instrument panel.

We thank you in advance for your kindness and remain,

Sincerely yours,

Dr.Ing.h.c.F.Porsche AG -Technical Administration-

Mayer

Dr.Ing.h.c.F.Porsche AG z. Hd. Herrn Mayer/ESV Postfach 11 40

7251 Weissach

WEST GERMANY