Interpretation ID: nht80-2.46

DATE: 06/06/80

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: International Harvester Company

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of April 30, 1980, asking whether a new electrical switch complies with S4.5.5 of Motor Vehicle Safety Standard No. 108.

As you have described it, the switch has three positions under two of which ("IGN/ACC" and "ACC") the hazard warning signals will operate. The third position, however, ("OFF") is a master switch which disconnects most electrical circuits on the vehicle including hazard warning signals. You have asked whether this design is permissible under S4.5.5 which requires the vehicular hazard warning signal operating unit to "operate independently of the ignition or equivalent switch." You have cited as precedent a 1972 letter from this agency to Imperial Fire Apparatus approving a battery disconnect switch design. In the 1972 system the hazard signals would only be activated by turning both the master switch and the flasher to "on". This was acceptable to NHTSA under paragraph 3(e) of SAE J910, Hazard Warning Signal Switch:

". . . providing the master switch is separate from the ignition switch and the hazard warning signal lamps will flash with the master switch on and the ignition switch off."

The principal difference between the two systems is that your switch "is a part of the ignition switch assembly and not physically located elsewhere on the instrument panel."

The intent of S4.5.5. is that the hazard warning signals operate regardless whether the ignition switch is on or off.

This intent would not appear to be met by your system whose master switch is part of the ignition switch assembly. We suggest, therefore, that you modify your design so that the hazard warning signal circuit is added to that of the "CB" and clock which remain operable when the master switch is in the "off" position.

SINCERELY,

INTERNATIONAL HARVESTER

April 30, 1980

Office of Chief Counsel National Highway Traffic Safety Administration US Department of Transportation SUBJECT: Ignition Switch with Master Off Position/FMVSS 108 S.4.5.5

Gentlemen: International Harvester Company (IH) is planning to introduce a new electrical switch on its new models. This switch incorporates a master "OFF" position which disconnects most electrical circuits on the vehicle. The OFF (master) switch performs essentially the same function as the one described in the attached interpretation #N41-34 dated August 11, 1972 except that it is a part of the ignition switch assembly and not physically located elsewhere on the instrument panel. This ignition switch has three positions "IGN/ACC", "ACC", and master "OFF". With the switch in the IGN/ACC position, the engine and accessories circuits are on. When the switch is turned to the "ACC" position, the engine is off and all accessories can be operated including the hazard warning flashers (key can be removed in this position). When the switch is turned to the master "OFF" position, all electrical circuits will be off except for the clock and "CB" circuits. These circuits must remain live so that the clock will continue running and the "CB" memory is maintained. Note that the switch can be turned from the "ACC" position to the "OFF" position or from the "OFF" position to the "ACC" position without a key. The key must be inserted to turn the ignition switch to engine run position ("IGN/ACC" position).

The purpose of this master "OFF" is to shut down most of the electrical circuits when the vehicle is not in use. This will protect the vehicle from power drains or fires due to electrical shorts when the vehicle is not in use. In addition, the vehicles electrical circuits can be shut off if a short is discovered by the driver while the vehicle is in use.

It is our opinion that this switch, which incorporates a master OFF is in compliance with FMVSS 108 S.4.5.5. We believe that it meets the intent of the standard of having the hazard flashers be operable when the engine is turned off and the key removed - (ACC position). We solicite the Agency's concurrence with this opinion.

This request is a follow-up to a telephone conversation of 4/21/80 between Mr. R. C. Hamilton and Mr. Z. Taylor Venson, who advised that we write this office for an interpretation. As mentioned by Mr. Hamilton, we are in dire need of a speedy reply as we are about to finalize this design for our new models.

Attached for your reference is a sketch illustrating the newly designed ignition switch assembly in question.

INTERNATIONAL HARVESTER COMPANY

F. L. Krall, Manager Technical Legislation

ATTACH.

cc: GEORGE L. PARKER

MASTER OFF SWITCH

OFF - (MASTER) - MOST SYSTEMS OFF (HAZARD FLASHERS WILL NOT OPERATE) ACC - ENG OFF & ACC ON (HAZARD FLASHERS AND ACCESSORIES WILL OPERATE)

IGN/ACC - ENG ON & ACC ON (HAZARD FLASHERS AND ACCESSORIES WILL OPERATE) (Graphics omitted)