Interpretation ID: nht80-4.16

DATE: 10/30/80

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Mazda

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. M. Ogata Branch Manager Mazda Toyo Kogyo U.S.A. Representative Office Detroit Branch 23777 Greenfield Road Southfield, Michigan 48075

Dear Mr. Ogata:

Thank you for your July 24, 1980, letter concerning your efforts to improve defogging performance. We share your concern about providing optimum driving visibility and are pleased with your efforts to improve this safety feature.

Your letter requested an interpretation of Federal Motor Vehicle Safety Standard 103, asking whether it is permissible to designate an intermediate blower fan speed (instead of the maximum speed) as the speed to be used when defrosting, if some caution or direction about the necessity for using that intermediate speed for defrosting purposes is provided in the Owner's Manual. The purpose of taking that step would be to cause the intermediate speed instead of the maximum blower speed to be used in testing the performance of the defrosting system under the standard. If this was permis- sible, you could increase the speed of the fan at the maximum position, thereby improving performance of the defogging function, while still being able to meet the performance requirements of the defrosting function at the intermediate speed (but not at the new maximum speed).

Paragraph S4.3 of the standard states that "the passenger car windshield defrosting and defogginq system shall be tested in accordance with the portions of paragraphs 4.1 through 4.4.7 of SAE Recommended Practice J902, August 1964, or SAE Recommended Practice J902a, March 1967, applicable to that system," with certain exceptions not applicable to your question.

Section 4.2(g) of SAE Recommended Practice J902 specifies as one of the testing conditions that the defroster system air be "On full. Blower on high." Similarly, section 4.2(g) of SAE Recommended Practice J902a specifies that the defroster system air be "On full. Blower on high speed." We therefore conclude that it would not be permissible under the standard as currently drafted to install a defrosting system which fails to meet the standard when the blower is set to its highest speed even if the system meets the standard at a lower blower speed and that lower blower speed is labeled as the maximum defrosting position. This conclusion would not be changed by the inclusion of directions in the Owner's Manual or words or symbols on the control panel.

If you are unable to resolve the problem in another way, i.e., improving the performance of the heating element, you may wish to petition the National Highway Traffic Safety Administration for an amendment to FMVSS 103. It is our inclination, however, that a defrosting system which operated optimally at a lower blower speed would cause considerable consumer confusion. Drivers would normally expect to obtain both optimum defrosting performance and optimum defogging performance at the highest blower speed. Even if the system was clearly labeled to indicate that the blower speed should be set to medium for defrosting and high for defogging, many consumers do not know the difference between defrosting and defogging. We would also have to consider the amendment's effect on Standard 101, since there is only one symbol for the defrosting and defogging system. If you should decide to petition for an amendment to Standard 103, we would like to see these issues addressed.

Sincerely,

Frank Berndt Chief Counsel

July 24, 1980 Our Ref. No.: DS-001

Chief Counsel National Highway Traffic Safety Administration 400 Seventh Street, S.W. Washington, D.C. 20590

Dear Sir,

Subject: Interpretation of FMVSS 103

After having a meeting with Mr. S. Oesch and Mr. G. Parker, they have requested that I should submit my questions to the chief counsel. These questions pertain to the testing condition of FMVSS 103. Your response would be appreciated before the end of August.

QUESTION

When we conduct the test to measure the defrosting performance which is required by FMVSS 103, is it permissible to designate the switch position of the blower fan motor to other than the maximum blower speed under the condition that we provide some caution or direction in the Owner's Manual?

BACKGROUND

1. Our current defrosting and defogging systems fan switch has four positions shown below.

*Insert Diagram

Generally speaking, there are relations between the volume of hot air and temperature of the hot air described below.

POSITION VOLUME OF AIR TEMP. OF AIR

HI Maximum Lowest

M less than HI higher than HI position position

L Minimum Highest

In addition, the defrosting performance depends on the temperature of the air rather than the volume of the air and the defogging performance depends on the volume of the air rather than the temperature of the air.

Therefore, we gave the defrosting performance which complies with FMVSS 103 with the fan switch in the HI position for all current vehicles.

However, we have customer complaints from the market that the defogging performance is relatively poor in the HI position. So, we are now considering to give more volume in the HI position to resolve this complaint which is very important performance while driving the car to receive the best visibility.

However, unfortunately, we can not comply with the requirement if we increase the volume of the air because of the decrease of the air temperature which is mentioned above.

Now we are considering to designate the position of the fan switch in the Owner's Manual such as:

"Turn the FAN SWITCH on M position to get the maximum defrosting performance"

This means that we increase the air volume on both the M and HI positions and we can comply the requirement in the M position instead of the HI position.

2. There are three documents concerning the testing condition for FMVSS 103. They are FMVSS 103, SAE J902 and the Laboratory Test Procedure (TP-103-09). There are some differences between these documents regarding the fan position shown below:

FMVSS 103: There is no definition concerning the position

SAE J903, Sec.J.4.2.7: On Full. Blower on high speed.

TP-103-09, 4(g): ...in the manufacturer's designated positions for optimum defroster performance.

So, please interpret this matter on whether our designation of the fan switch position is acceptable.

In addition, please give us the information as to what kind of statement is acceptable in the Owner's Manual and whether we have to provide some words or symbols on the control panel from the point of FMVSS 101.

Thanking you in advance,

Sincerely yours,

M. Ogata Branch Manager

cc: Mr. G. Parker Office of Vehicle Standards Crash Avoidance Division