FMVSS 104: Windshield Wiping and Washing explained.

What FMVSS 104 says it is for

The eCFR heads this section "Standard No. 104; Windshield wiping and washing systems." Under 49 CFR part 571, the Federal Motor Vehicle Safety Standards are the numbered standards that set safety performance requirements for motor vehicles and equipment. The text below is quoted from 571.104 as current through October 29, 2026.

This standard specifies requirements for windshield wiping and washing systems.

What it applies to

The application section of the standard says:

This standard applies to passenger cars, multipurpose passenger vehicles, trucks, and buses.

Applicability is decided by the text of the standard as written, including any exclusions it lists, and by the date-specific rules in it. This page does not decide whether a particular vehicle or item is covered.

How the standard is organized

The eCFR text of 571.104 has these top-level sections:

• S1: Scope
• S2: Application
• S3: Definitions
• S4: Requirements

In all, the text has 10 numbered headings. Use the finder above to search them; for example, a search for "test" lists the headings that mention tests.

Key requirements, quoted from the text

These are excerpts from the requirements sections of 571.104, in the order the standard presents them. Long paragraphs are shortened where marked with [...]; the eCFR has the complete text, tables and figures, which this page omits.

S4.1 Windshield wiping system. Each vehicle shall have a power-driven windshield wiping system that meets the requirements of S4.1.1.

S4.1.1.2 One frequency or speed shall be at least 45 cycles per minute regardless of engine load and engine speed. S4.1.1.3 Regardless of engine speed and engine load, the highest and one lower frequency or speed shall differ by at least 15 cycles per minute. Such lower frequency or speed shall be at least 20 cycles per minute regardless of engine speed and engine load. S4.1.1.4 Compliance with subparagraphs S4.1.1.2 and S4.1.1.3 may be demonstrated by testing under the conditions specified in sections 4.1.1 and 4.1.2 of SAE Recommended Practice J903a (1966) (incorporated by reference, see § 571.5).

S4.1.2 Wiped area. When tested wet in accordance with SAE Recommended Practice J903a (1966) (incorporated by reference, see § 571.5), each passenger car windshield wiping system shall wipe the percentage of Areas A, B, and C of the windshield (established in accordance with S4.1.2.1) that (1) is specified in column 2 of the applicable table following subparagraph S4.1.2.1 and (2) is within the area bounded by a perimeter line on the glazing surface 25 millimeters from the edge of the daylight opening. S4.1.2.1 Areas A, B, and C shall be established as shown in Figures 1 and 2 of SAE Recommended Practice J903a (1966) (incorporated by reference, see § 571.5) using the angles specified in Columns 3 through 6 of Table I, II, III, or IV, as applicable.

S4.2 Windshield washing system. S4.2.1 Each passenger car shall have a windshield washing system that meets the requirements of SAE Recommended Practice J942 (1965) (incorporated by reference, see § 571.5), except that the reference to “the effective wipe pattern defined in SAE J903, paragraph 3.1.2” in paragraph 3.1 of SAE Recommended Practice J942 (1965) shall be deleted and “the areas established in accordance with subparagraph S4.1.2.1 of Motor Vehicle Safety Standard No. 104” shall be inserted in lieu thereof. [...]

Defined terms

The standard defines 7 terms in its definitions section; the first 7 are quoted here from the eCFR.

• The term seating reference point is substituted for the terms manikin H point, manikin H point with seat in rearmost position and H point wherever any of these terms appear in any SAE Standard or SAE Recommended Practice referred to in this standard.
• Daylight opening means the maximum unobstructed opening through the glazing surface, as defined in paragraph 2.3.12 of section E, “Ground Vehicle Practice,” of SAE Aerospace-Automotive Drawing Standards (1963) (incorporated by reference, see § 571.5).
• Glazing surface reference line means the line resulting from the intersection of the glazing surface and a horizontal plane 635 millimeters above the seating reference point, as shown in Figure 1 of SAE Recommended Practice J903a (1966) (incorporated by reference, see § 571.5).
• Overall width means the maximum overall body width dimension “W116”, as defined in section E, “Ground Vehicle Practice,” of SAE Aerospace-Automotive Drawing Standards (1963) (incorporated by reference, see § 571.5).
• (ii) A line parallel to the vehicle longitudinal centerline located so that the geometric center of the 95 percent eye range contour is positioned on the longitudinal centerline of the driver's designated seating position.
• Shoulder room dimension means the front shoulder room dimension “W3” as defined in section E, “Ground Vehicle Practice,” of SAE Aerospace-Automotive Drawing Standards (1963) (incorporated by reference, see § 571.5).
• 95 percent eye range contour means the 95th percentile tangential cutoff specified in SAE Recommended Practice J941 (1965) (incorporated by reference, see § 571.5).

Limits of this page

This page quotes the text of 49 CFR 571.104 as published in the eCFR, current through October 29, 2026. It omits tables, figures, cross-referenced test procedures in other parts, and the preambles and rulemaking history that explain the rule. It does not tell you whether a given vehicle, part or product complies, how to run a test, or what a manufacturer must certify. Compliance questions go to the manufacturer's engineers, qualified counsel or NHTSA. The eCFR is an editorial compilation, not the official legal edition of the Federal Register.

Sources

Sources opened and read November 2, 2026.

• eCFR: 49 CFR 571.104, Standard No. 104; Windshield wiping and washing systems. (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR part 571, Federal Motor Vehicle Safety Standards (current through October 29, 2026) (read November 2, 2026)