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Headlamps — Sealed Beam, Replaceable Bulb & LED

Vehicle headlamps are either sealed beam units, housings with a replaceable bulb, or integral LED assemblies. This sheet covers how to tell them apart, the common trade numbers and the FMVSS 108 points that matter at the counter.

Ref FA-0019FMVSS 108

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Every headlamp sold for on-road use in the United States must meet FMVSS 108. There are three system types. A sealed beam is one sealed unit: lens, reflector and light source together, replaced as a whole. A replaceable bulb headlamp has a housing and lens that stay on the vehicle and a bulb that twists or clips into the back. An integral LED headlamp has LED sources built into the assembly, and the whole lamp is replaced. Many heavy trucks and older vehicles use standard sealed beam sizes, so LED replacements are sold in those same sizes.

How to identify

Measure the lens face and note the shape: round or rectangular. Read the trade number molded on the lens or printed on the back. Look for "DOT" on the lens; a compliant lamp carries it. For bulb-type lamps, the bulb number is on the bulb base or in the owner's manual. Low beam, high beam and dual beam units are not interchangeable, even in the same size.

Common types and trade numbers

Type	Common trade numbers	Notes
7 in round sealed beam	6014, H6024	Dual beam; H prefix means halogen
5-3/4 in round sealed beam	4000 / H5006 (dual), 4001 / H5001 (high only)	Used in four-lamp systems
4 x 6 in rectangular sealed beam	H4656 (dual), H4651 (high only)	Common on trucks and trailers
5 x 7 in rectangular sealed beam	H6054	Dual beam
Replaceable bulb, dual filament	H4 (9003), H13 (9008)	One bulb gives low and high
Replaceable bulb, single filament	H1, H3, H7, H11, 9005 (HB3), 9006 (HB4)	Separate bulbs for low and high
Integral LED	Vehicle-specific part numbers	Whole assembly replaced

Key points

Match the trade number, not just the size. A high-only unit in a low-beam position fails inspection.
FMVSS 108 compliance applies to the whole lamp. An aftermarket LED bulb in a housing designed for a halogen bulb is generally not a compliant combination, whatever the package says.
LED sealed beam replacements in standard sizes should carry DOT marking and SAE beam codes.
On LED conversions, check for flicker or warning lights on vehicles that monitor bulb current.
Aim headlamps after replacement. Most lamps have aim marks such as VOL or VOR molded in.

Common mistakes

Selling a single-beam unit when the vehicle uses dual-beam lamps.
Selling an LED bulb for a halogen reflector housing as a road-legal upgrade.
Ignoring aim after a lamp change.
Mixing halogen and LED lamps on one vehicle so the beams do not match.

Governing standards: FMVSS 108 (49 CFR 571.108), lamps, reflective devices and associated equipment. See the FMVSS 108 lamp color and placement chart for other lamp functions.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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