ID: nht74-5.56

DATE: 06/06/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Hellstar Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of May 13, 1974, requesting information concerning the existence of any Federal Motor Vehicle Safety Standards applicable to auxiliary fuel tanks.

The National Highway Traffic Safety Administration has promulgated no motor vehicle safety standard relating to auxiliary fuel tanks. There is, however, a safety standard which imposes performance requirements upon motor vehicles with regard to their fuel systems. Thus, if installation of the auxiliary tank is accomplished prior to the first purchase of the vehicle for purposes other than resale causing the vehicle's fuel system not to be in compliance with the applicable safety standard, the person installing the tank or offering the vehicle for sale would be in violation of @ 108(a)(1) of the National Traffic and Motor Vehicle Safety Act. That would make the installer or seller subject to civil penalties of up to $ 1,000 for each violation.

The National Traffic and Motor Vehicle Safety Act authorizes the Secretary of Transportation to make a determination as to whether or not an item of motor vehicle equipment contains a defect which relates to motor vehicle safety. If he finds that a safety-related defect exists, he may compel the manufacturer to notify purchasers of the hazard. Therefore, even though auxiliary fuel tanks are not the subject of a standard, they still must be safely designed.

For your information, I have enclosed a copy of the Federal Safety Standard relating to motor vehicle fuel systems.

Enc.

HELLSTAR CORPORATION

May 13, 1974

U. S. Department of Transportation National Highway Traffic Administration

Hellstar is making auxilary gas tanks for pickups, which is added to the pickup after manufactured from original manufacturer.

What are the regulations and what standards do we have to meet? Is there any test requirement necessary?

Merle O. Roberts Controller

ID: nht74-5.57

DATE: 05/15/74

FROM: LAWRENCE R. SCHNEIDER -- CHIEF COUNSEL, NHTSA

TO: PETER J. PITCHESS -- SHERIFF, COUNTY OF LOS ANGELES,

TITLE: NONE

TEXT: This is in response to your letter of May 2, 1974, requesting the results of the public hearing concerning safety standards for police vehicles held on December 10, 1973, and your petition in this regard.

As you know, that hearing was held in conjunction with an advance notice of proposed rulemaking issued by this agency. We are in the final stage of analysis of both the public bearing and the comments in response to the advance notice, and will issue our conclusions in the near future. In the interim, all Federal Safety Standards continue to be applicable to police vehicles although you remain free to alter your vehicles after they are delivered to you.

ID: nht74-5.6

DATE: 02/20/74

FROM: AUTHOR UNAVAILABLE; Lawrence R. Schneider; NHTSA

TO: Douglas F. Welebir, Esq., Attorney at Law

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of December 28, 1973, File No. 1041, requesting information on the Federal installation requirements for safety belts in a 1971 Toyota Land Cruiser.

Federal Motor Vehicle Safety Standard No. 208, Occupant Crash Protection (formerly titled "Seat belt installation"), required safety belts in all designated seating positions of all passenger cars manufactured on or after January 1, 1968. Similar requirements were instituted for trucks and multipurpose passenger vehicles manufactured after July 1, 1971. The Toyota Land Cruiser is classified as a multipurpose passenger vehicle. If it were manufactured before July 1, 1971, no installation requirement would have applied. It should be noted that seat belts were not factory-installed in some Land Cruisers, and we know of one Arizona dealer who failed to install seatbelts in a Land Cruiser built after that date.

In answer to your second question, the Land Cruiser did not have any exemption under 15 U.S.C. @ 1410 or any other section of the Act.

ENC.

December 28, 1973

Director National Highway Safety Bureau

I represent a young man injured in an automobile accident primarily because of the lack of seat belts in a 1971 Toyota Land Cruiser. Would it be possible to obtain a copy of the vehicle safety standards enacted pursuant to the National Traffic and Motor Vehicle Safety Act of 1966 relating to the installation of seat belts in new automobiles.

I would also appreciate knowing whether or not Toyota Motor Company of the United States has been exempt from compliance with this Act under 15 USC 1410 or any other section.

I thank you for your assistance and helpfulness in this important matter.

DOUGLAS F. WELEBIR

ID: nht74-5.7

DATE: 04/01/74

FROM: AUTHOR UNAVAILABLE; Lawrence R. Schneider; NHTSA

TO: Charles F. Aycock

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of February 16, 1974, asking whether courtesy lights for trucks carry the message "clear" and "thanks" are in violation of any Federal regulations. The courtesy lights to which you refer in your letter do not violate any regulation of the National Highway Traffic Safety Administration. We have forwarded a copy of your letter to the Bureau of Motor Carrier Safety in the Federal Highway Administration for a response in regard to the motor carrier safety regulations.

ALDRIDGE, HARDING & AYCOCK

FEBRUARY 16, 1974

LAWRENCE SCHNEIDER -- CHIEF COUNSEL, DEPT. OF TRANSPORTATION

RE: COURTESY LIGHTS

I represent Tom Paine, of Bovina, Texas, who has developed a lighting system for large tractor-trailer vehicles and a patent is now pending on same.

During the course of developing the product we were advised to contact the American Association of Motor Vehicles to obtain their Certificate of Approval in the 47 states represented by the Association. We are now in the process of filing that application, and on this date I discussed same with Mr. Frank Bergsman, in your office of Standards and Enforcement. Mr. Bergsman suggested that we write to you regarding the legality of the use of the product insofar as any Federal regulations are concerned.

Specifically, the courtesy lights are a set of two lights, one of which is a green light with the word "clear" stamped on the lens. The other light is a blue light with the word "thanks" stamped in the lens. The green light goes on the front of the motor vehicle and when a truck passes the vehicle with the green light on the front the operator of the vehicle being passed simply turns a toggle switch which activates the green light that may readily be seen in the rear view mirrow of the passing trucker. Of course, the purpose of this light is to show the passing trucker that his trailer has cleared the vehicle he is passing. The lens which go on the back of the truck would simply be a 'thank you' device which may also be activated by a simple toggle switch.

I am enclosing a copy of the Application filed in the

2 Patent Office with the describing pictures, which I think will make the purpose of the units more clear. My client was a trucker for many years, and during the course of driving trucks noted that truckers wore out many sets of head lights and clearance lights blinking them off and on as a courtesy gesture to passing vehicles. His product simply is designed to avoid those problems.

Specifically, we cannot find anything in the motor carrier safety regulations as revised, including the amendments, that prohibits the use of said equipment. We were, however, wanting an opinion from your office as to whether or not we would be in violation of any Federal safety regulation if these products were manufactured and placed on motor carrier vehicles.

We do understand that there are certain state jurisdictions that we will have to obtain permission from before selling the product in that state. We will proceed to obtain that jurisdiction, but we want to satisfy ourselves that we were completely in compliance with any Federal statutes or regulations.

Your assistance and opinion would surely be appreciated, and we would look forward to hearing from you as quickly as possible. If you have any questions please do not hesitate to contact me.

CHARLES F. AYCOCK

ENCL.

Graphics omitted)

THOMAS G. PAINE

THRU: CHARLES F. AYCOCK

COURTESY LIGHT FIXTURE

ABSTRACT OF THE DISCLOSURE

A visual signaling system for large trucks passing each other while traveling in the same direction, after nightfall. Each vehicle mounts a pair of signal lamps adjacent the front and rear ends which lamps are illuminated under control of the driver to signal another vehicle or acknowledge receipt of a signal.

This invention relates to signaling systems for relatively large road vehicles such as trailer trucks.

One of the hazards encountered during nighttime motor vehicle travel, is difficulty in judging distances. This problem arises in particular when one vehicle passes another while traveling in the same direction and after passing moves laterally into the right-hand lane from the left-hand passing lane. Before moving back to the right-hand lane, a driver of a passing vehicle should be certain that there is sufficient clearance between his vehicle and the vehicle just passed. Judging such clearance is particularly difficult in connection with relatively long trucks such as tractor cabs with trailers hitched thereto. It is current practice in such vehicle passing situations, for the driver of the vehicle being passed to momentarily turn on the high beams of the headlamps which are reflected in the rear view mirror of the passing vehicle in order to signify to the driver that his vehicle has cleared the front end of the vehicle being passed. It is therefore an important object of the present invention to provide a signaling system to more positively and reliably take care of the foregoing situation in which the drivers of two vehicles wish to communicate with each other.

In accordance with the present invention, large vehicles such as elongated trucks are provided with a pair of signal lamps adjacent the front and rear ends thereof, said lamps being provided with bulb covers of different colors having faces on which a message is made visible by illumination of the lamp. Illumination of the lamp adjacent the front end is effected under control of the vehicle driver within the cab in order to signal the driver of a passing vehicle that his vehicle has cleared the front end of the vehicle being passed. The lamp mounted adjacent the front end may accordingly bear the letters "Clear" that become visible to the driver in a passing vehicle through the rear view mirror when the lamp is illuminated. The rear end mounted signal lamp, on the other hand, is provided with lattering such as "Thanks" so that the driver of the passing vehicle may acknowledge receipt of the "Clear signal by illuminating the rear mounted lamp. The illumination produced by the two lamps is of different colors so that the messages may be readily distinguished from each other at a glance.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

Figure 1 is a simplified top plan view of a pair of road vehicles in a passing situation, the vehicles being provided with the signaling system of the present invention.

Figure 2 is a perspective view illustrating one of the signal lamps associated with the system of the present invention.

Figure 3 is a perspective view illustrating the other of the lamps associated with the signaling system.

Figure 4 is a longitudinal sectional view through one of the lamps.

Figure 5 is a simplified electrical circuit diagram corresponding to the system of the present invention.

Referring now to the drawings in detail, Figure 1 illustrates a typical two lane road generally referred to by reference numeral 10 on which vehicles travel in the same direction. A vehicle generally referred to by reference numeral 12 traveling in the right-hand lane is accordingly shown being passed by another vehicle generally referred to by reference numeral 14 traveling in the same direction in the left-hand or passing lane. As is well known, the passing lane is only used during the passing maneuver and the passing vehicle will return to the right-hand traveling lane after passing another vehicle, with sufficient clearance. Figure 1 illustrates this passing situation wherein the passing vehicle has cleared the vehicle 12 being passed.

The system of the present invention is shown installed on relatively long vehicles which include, for example, a tractor cab 16 at the front end to which a trailer 18 is hitched. Each vehicle mounts a pair of signal lamps including a signal lamp 20 mounted adjacent the front end of the vehicle and a signal lamp 22 mounted adjacent the rear end of the vehicle. When the passing vehicle 14 has cleared the vehicle 12, as shown in Figure 1, the driver of the vehicle 12 will cause signal lamp 20 thereon to be illuminated producing illumination 24 emitted forwardly therefrom, which will be observed by the driver of the passing vehicle 14 through the rear view mirror. This signal will then be acknowledged by the driver of the vehicle 14 by causing the rear mounted signal lamp 22 to be illuminated producing illumination 26 emitted rearwardly therefrom.

Each of the signal lamps 20 and 22 is similar in construction and operation to each other except for the signaling indicia and color of it light transmitting cover 28 as shown in Figures 2, 3 and 4. Each lamp includes a relatively rigid base 30 adapted to be fixedly mounted on the vehicle. The base includes a relatively flat, rectangular reflective portion 32 from which a peripheral flange 34 extends rearwardly terminating in a seating rim 36 adapted to abut the surface of the vehicle. Extending from the front face 38 of the cover 28, is a peripheral rim 40. The rim 40 of the cover is provided with a plurality of spaced projections 42 adapted to be snapped into retainer openings 44 formed in the flange portion 34 of the base 30. A sealing gasket 46 is sandwiched between the rims 36 and 40 of the base and cover, when the cover is assembled on the base as shown in Figure 4. Ventilation holes 48 are formed in the flat reflective portion of the base so as to permit dissipation of heat generated within the space 50 enclosed by the cover.

A pair of incandescent bulb assemblies 52 are mounted on the reflective portion 32 of the base within the space 50 in order to emit illumination through the colored cover 28 on which the signal indicia is mounted as shown in Figures 2 and 3. Electrical conductors extend from the bulb assemblies 52 through a central opening in the base lined by a nonconductive grommet 54.

As shown in Figures 2 and 3, the indicia mounted on the cover of lamp 22 is in the form of letters spelling "Clear" in order to signify that a passing vehicle has sufficiently cleared another vehicle as shown in Figure 1. The lamp 20 on the other hand is provided with indicia on its cover which spells "Thanks" thereby acknowledging receipt of the "Clear" signal. The lamps may be selectively controlled by the driver in a vehicle from the cab by means of switches 56 and 58 as shown in Figure 5 which thereby complete parallel lighting circuits through the associated lamps connected, for example, to the vehicle battery 60.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In combination with an elongated, road vehicle having front and rear ends, a signaling system comprising, a pair of lamps respectively mounted adjacent the front and rear ends of the vehicle, and means for selectively illuminating said lamps to signal another vehicle traveling in the same direction, the lamp on the front end bearing indicin signifying clearance in the direction of travel and the lamp on the rear end bearing acknowledgment indicia.

2. The combination of claim 1 wherein said lamps respectively include covers of different colors.

3. The combination of claim 2 wherein each of said lamps includes a relatively rigid base having a substantially flat reflective surface and a rim portion provided with retainer openings, each of said covers having a peripheral flange provided with projections received within said retainer openings, and incandescent bulb means mounted on the reflective surface enclosed within the cover.

4. The combination of claim 1 wherein each of said lamps includes a relatively rigid base having a substantially flat reflective surface and a rim portion provided with retainer openings, a cover having a peripheral flange provided with projections received within said retainer openings, and incandescent bulb means mounted on the reflective surface enclosed within the cover.

5. The combination of claim 4 wherein the cover for the lamp adjacent the front end is colored green as background for the indicin "clear", while the cover for the lamp on the rear end is colored blue as background for the indicia "thanks".

6. The combination of claim 1 wherein said lamps include light transmitting covers respectively colored green and blue, the indicia on the cover for the front end mounted lamp reading "clear" while the indicia on the cover for the rear end mounted lamp reading "thanks".

ID: nht74-5.8

DATE: 02/21/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Bridges and Collins

TITLE: FMVSR INTERPRETATION

TEXT: In reply to your request of January 30, 1974, I am enclosing a copy of the regulation issued to implement the odometer disclosure requirements of Public Law 92.513.

Although there are a variety of ways to determine whether a vehicle's actual mileage is greater than shown on the odometer, I know of only one method to establish the exact amount by which the indicated mileage has been exceeded: the testimony of a witness who knew the exact mileage on the car at the time the odometer was changed and who knows the accuracy of the odometer's performance after the change.

I would be most interested to learn of the progress of your action.

BRIDGES AND COLLINS

January 30, 1974

Department of Transportation National Highway Traffic Safety Administration

IN RE: Odometer Disclosure Requirements

Dear Administrator:

I am at the present time attempting to prosecute a civil action under Section 408 (a) of Title IV of the Motor Vehicle Information and Cost Savings Act (Public law 92-513). (This statute may be found in 15 U.S.C.A. @ 1988.)

Please send me a copy of the current rules regulating this statute.

I am having some difficulty determining the true mileage of the vehicle in question. If you know of a procedure for determining the actual mileage of a motor vehicle, please pass that information along to me. I would be most appreciative.

I can use the above-requested information as quickly as you can supply it.

Thank you for your prompt assistance and cooperation.

James B. Steward

ID: nht74-5.9

DATE: 01/18/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: John W. Davis; House of Representatives

TITLE: FMVSR INTERPRETATION

TEXT: This is in reply to your letter of December 17, 1973, on behalf of Ms. Judith Davis, who has suggested the incorporation of the Federal odometer form into the bill of sale as a means of reducing paperwork in motor vehicle transactions.

Although the Federal odometer disclosure regulation requires the seller to give the buyer several items of information that we consider essential to adequate disclosure, the regulation does not require the use of a separate form. If Ms. Davis is able to include the required information in the bill of sale used by the Rome Auto Auction, she may do so. Information items that are common to the bill of sale and the disclosure statement, such as the model and make of the vehicle, would not have to be stated twice.

Enclosures

ID: nht75-1.1

DATE: 11/26/75

FROM: AUTHOR UNAVAILABLE; James B. Gregory; NHTSA

TO: Libby-Owens-Ford Company

TITLE: FMVSS INTERPRETATION

TEXT:

N41-42

H. M. Alexander, Vice President Technical Development & Services Libbey-Owens-Ford Company 1701 East Broadway Toledo, Ohio 43605

Dear Mr. Alexander:

This is a further reply to your letter of September 11, 1975, requesting an interpretation of the test procedures for measuring light transmission of glazing materials in accordance with Federal Motor Vehicle Safety Standard No. 205, Glazing Materials.

As you know, the purpose of the luminous transmittance requirement is to assure that safety glazing used in motor vehicles at levels requisite for driving visibility, does not restrict the vehicle operator's vision below that necessary for safe operation. Further, the apparent effective luminous transmittance of safety glazing as viewed by the human eye is the average transmittance of the entire area surveyed by the eye. In view of this, the National Highway Traffic Safety Administration would not consider glazing with an average luminous transmittance over its entire area of 70 percent or more to be in non-compliance with the standard.

As you pointed out, the luminous transmittance test procedure specified by Standard No. 205 does not specify the diameter of the measuring light beam. Thus, you are free to use any diameter light beam that is appropriate.

In regard to the distinct bend lines in your back window, we would consider for purposes of determining luminous transmittance, your back window to be divided into three sections - two wings and the central section. Thus, in this case, the distinct bend lines would not be considered as glazing material.

Sincerely,

James B. Gregory Administrator

September 11, 1975

Dr. James B. Gregory, Administrator National Highway Traffic Safety Administration Nassif Building Washington, D.C. 20590

Dear Dr. Gregory:

On August 25, we met at the Department of Transportation with Messrs. Guy Hunter, Doug Pritchard and Chuck Kaehn and discussed a new type automotive backlight.

This new type backlight offers advantages toward greater safety by better rear visibility with minimal optical distortion. However, we questioned whether this type backlight meets the 70% light transmission requirement of the ANSI Code Z26 which is a requirement of FMVSS 205.

This new backlight achieves its advantages as the result of bending sharply around a "hot line" electrical conductor which results in a .190" wide opaque line at the boundary between the intersecting bent glass surfaces. In the heated version of such a backlight, the conducting lines in the wing areas are only 17/32" apart whereas in the central area of the backlight, the lines are 1-1/8" apart. See attached sketch of "hot line bent" back window dated September 5, 1975.

The ANSI Code which requires that such an automotive backlight have a light transmission above 70%, does not specify the diameter of the measuring light beam or its placement on the backlight. In the backlight discussed here, if a 1-1/4" diameter measuring beam is used and positioned with one heating line centered in the beam in the central or major rear vision area, it meets the 70% requirement, see Figure 1 in the attached memorandum by Paul Mattimoe dated September 5, 1975. However, if two heating lines are located symmetrically within the same beam as shown in Figure 3 in attached memo, the transmission does not meet the code requirement.

Therefore, we respectfully request that the NHTSA provide an interpretation which will recognize that this improved design of backlight meets the intent of FMVSS 205. Specifically we would suggest that the interpretation specify the positioning of one frit conductor line centered in the light beam as shown in Figure 1 of the attachment. This orientation will provide additional objectivity in the test conditions while the 70% transmissibility requirement will continue to limit the amount of abscuration which could be caused by the electrical conductors. In addition, we suggest that transmission measurements should not be required at the boundaries formed by the intersection of any two glazing surfaces.

We will appreciate your consideration of this request. We will be glad to meet at DOT offices again if advisable. It is urgent that a decision be received since production tooling for the car model involved in this request is proceeding at the present time.

Very truly yours,

H. M. Alexander Vice President Technical Development & Services

HMA:pjp

Attachments

ID: nht75-1.10

DATE: 12/17/75

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: British Leyland Motors Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your October 20, 1975, letter concerning the status of amendments to Federal Motor Vehicle Safety Standard No. 101, Control Location, Identification and Illumination, that were proposed in Notice 10 (Docket 1-18, 38 FR 26940, September 27, 1973).

Although a further proposal on this subject is being considered, no final decision has been made by the National Highway Traffic Safety Administration (NHTSA) concerning action on the outstanding proposal. You should be guided by the standard in its present form. The effective date of any amendments issued by the NHTSA will allow adequate lead time for compliance.

YOURS TRULY,

October 20, 1975

Office of General Counsel National Highway Traffic Safety Administration

On 27 September, 1973, Docket 1-18, Notice 10 proposed several changes to FMVSS 101. One specific change proposed the use of ISO symbols in lieu of the current 101 symbols.

Notice 11, issued 29 July, 1975, amended the Standard in respect of the ISO symbols alone. It made, however, no reference whatsoever to the remaining proposals of Notice 10.

We are presently negotiating with our supplier for new instruments for 1977 model year vehicles. We propose to identify the fuel, oil pressure and temperature guages with ISO symbols rather than words, as this would allow commonization between European and USA guages. While the symbols we propose for these guages are not prohibited at the present time, we are concerned that the words proposed in Table 2, Notice 10 might be implemented.

Are steps being taken on the Notice 10 proposals or may we proceed with ISO symbols with confidence that NHTSA will propose ISO symbols for all controls mentioned in Notice 10 at some future time.

BRITISH LEYLAND MOTORS INC.

Dianne Black Liaison Engineer

ID: nht75-1.11

DATE: 08/25/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: American Honda Motor Co., Inc.

TITLE: FMVSS INTERPRETATION

TEXT: I am writing to confirm your telephone conversation of August 4, 1975, with Mark Schwimmer concerning the applicability of Federal Motor Vehicle Safety Standard No. 101, Control Location, Identification and Illumination, to an intermittent-operation windshield wiper switch.

Your letter of June 4, 1975, described such an intermittent operation switch which is distinct from the normal windshield wiper switch. As Mr. Schwimmer explained, Standard No. 101 requires neither illumination nor any particular location for this intermittent switch, because the normal switch is already subject to all of the standard's requirements.

SINCERELY,

June 4, 1975

Richard B. Dyson NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

This is to request your official interpretation as to the applicability of Federal Motor Vehicle Safety Standards in the case of an 'intermittent-operation' windshield wiper switch. The switch would be offered as a dealer installed option and is intended for use when driving in light rain.

I am enclosing photographs showing the recommended switch positions, photo A shows placement on vehicles fitted with air conditioning, photo B is without airconditioning. The location of the standard wiper switch is shown in both photos.

The optional switch has a non-illuminated control knob identified by a windshield wiper symbol and the letters 'INT'.

The switch will cause the wipers to operate intermittently, one stroke across the windshield and back to the parked position, at intervals ranging from 2 to 10 seconds depending upon the degree of rotation of the control from the 'ON' position. The intermittent operation switch will operate the wipers when the standard wiper switch is in the 'OFF' position; switching ON the standard switch will over-ride the intermittent operation.

I would appreciate your early response on this matter. Please contact me if you need further information.

AMERICAN HONDA MOTOR CO., INC.

Brian Gill Assistant Manager Safety & Environmental Activities (Graphics omitted)

ID: nht75-1.12

DATE: 07/08/75

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Mercedes-Benz of North America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your letter of May 5, 1975, asking at what point the test voltage may be measured during testing for compliance with the Standard No. 103, Windshield Defogging and Defrosting Systems, requirement that the blower motor test voltage be 15% over nominal system rating at the blower motor or the supply end of the motor dropping resistor. Your question relates to the meaning of "the supply end of the motor dropping resistor."

Measurement of the blower motor test voltage should occur at the supply side of the motor where there is no resistor. Where the system contains a resistor, the voltage should be measured at the supply side of the resistor, not between the resistor and the motor. The reason for this is that the test voltage level specified in the standard is intended to relate only to the voltage as it is fed into the defrosting and defogging system. The purpose of the voltage level specification is to assure a system capability to handle voltage levels that will normally be encountered during operation of the defroster and defogger. This can be accomplished by measurement of the voltage before the current reaches the resistor.

Yours Truly,

MERCEDES-BENZ OF NORTH AMERICA. INC.

May 5, 1975

National Highway Traffic Safety Administration

Subject: Request for Interpretation; Federal Motor Vehicle Safety Standard 103 - Windshield Defrosting & Defogging Systems

FMVSS 103 through reference to SAE J902, requires that the blower motor test voltage be 15% over nominal system rating at the blower motor (for example 13.8 volts on the 12 volt system) or the supply end of motor dropping resistor.

The terminology "the supply end of motor dropping resistor" does not, in our opinion, provide specific direction on the test methods to be used for designing to this Standard. We would appreciate receiving clarification as to whether or not the test voltage may be measured at:

1. the motor,

2. the circuit between the dropping resistor and the motor, or

3. the dropping resistor on the side of the electrical power source.

We recommend that the requirements be interpreted to mean that the test voltage shall be measured at the motor or before the dropping resistor if included in the defroster motor circuit.

Permitting the use of a dropping resistor in the defroster motor circuit permits the designer to provide exact blower motor speeds for this function. Should, however, this resistor be excluded during compliance testing, the higher voltage at the motor would result in higher fan speeds, which might result in less than optimum deicing of the windshield.

Should you require any additional information concerning this request, do not hesitate in contacting this office.

Heinz W. Gerth

Assistant Vice President

Engineering