Rick's Free Auto Repair Advice

Retrofit LED headlight bulbs

Should you install retrofit LED headlight bulbs?

No, for several reasons. First, It’s illegal to retrofit LED headlight bulbs into a headlight assembly designed for halogen bulbs. Second, they actually throw LESS light on the road, despite the fact that they output more lumens than a traditional halogen bulb.

But they sell LED headlight bulbs everywhere

Hey, it is not illegal to manufacture and sell retrofit LED bulbs It’s just illegal to install them in a headlight assembly designed for halogen bulbs. Look anywhere in auto parts stores or online and you’ll find a huge assortment of retrofit LED headlight bulbs. They don’t require any wiring modifications, fit into your existing headlight assemblies, and they tout much higher lumen output. Sounds too good to be true, right. Well, it is.

Are retrofit LED bulbs legal?

No, not if they’re installed in a headlight that’s been certified for halogen bulbs. They can only be installed in a headlight assembly designed and certified for use with LED bulbs. D.O.T certified headlights that were designed for halogen bulbs meet Federal lighting standards for beam focus and light output. Those Federal regulations aren’t just some namby pamby rules. They’re in place for a reason. If you ignore this and install LED bulbs and the glare from those bulbs interfere with another driver’s vision, causing an accident, YOU will be held liable.

Will LED bulbs produce more light ON THE ROAD

No. Here’s where the irony comes into play.

LED headlight bulb

Multiple diodes=Multiple focal points=light scatter and glare

LED bulbs DO produce more lumens than a standard halogen bulb. However, because they generate the light from multiple circuit-on-board (COB) LEDs placed in various places on the bulb frame, most of the light they produce never makes it onto the road. Why? Because the reflector in your halogen headlight was designed for a bulb with a single hot spot placed at a certain distance from the reflector. It’s call a single focal point reflector and its job is to reflect the light in a certain pattern. See the patterns below.

When you install an LED bulb with multiple hot spots, most of those extra light sources won’t be reflected properly, not even in a projector headlight assembly. The projector lens simple can’t compensate for light scatter coming off the reflector. Simply put, it can properly focus light that comes into the lens from the wrong angles. So since the LED light source located closest to the halogen focal point is the light that will be concentrated by the projector lens. In other words, if you install retrofit LED bulbs in your old halogen headlight assembly, you’ll cast LESS light on the road and cause more glare into oncoming vehicles.

headlight replacement cost

Proper filament placement provides optimum light output and beam pattern








HID conversion kit

When the filament position changes, so does the beam pattern














Here’s where the illegal parts comes in

The Department of Transportation has rigorous standards for headlight assemblies. The regulations detail the beam pattern required for high and low beams. Once a headlight assembly is designed and approved for a particular type of bulb, it is illegal to retrofit it with a different bulb. Read the D.O.T letter at the end of this story and read about the legal liability issue here. The lawsuit mentioned is about tail-lights, but the liability issue is the same: If you change the lighting from factory and it causes an accident you are liable.

Many people buy retrofit LED bulbs that claim they’ll fit into existing headlight assemblies. Well, they may fit, but they’re not legal if the original assembly was approved for halogen bulbs.


When you get caught by the law

Because the beam pattern is different than the halogen bulbs, retrofit LED  bulbs often cause glare to oncoming traffic and THAT’s how you get caught by the police. The glare gives you away.


Retrofitting with LED exposes you to legal liability

The glare you throw into oncoming traffic can cause accidents. If your LED retrofit bulbs cause glare and that glare causes an accident, YOU can be sued for not having compliance headlights. Oregon State Police Senior Trooper Douglas Brown states, “I’ve had cases where they’ve swerved across into the oncoming lanes and hit the car that was blinding them.”

LED bulbs are notoriously unreliable

LED bulbs have large cooling fins that extend outside the headlight assembly. Some LED bulbs have fans to help cool the electronics. They’re far more expensive to buy and they tend to fail faster than standard halogen bulbs. Put it all together; less light on the road, more glare for oncoming traffic, higher cost and shorter life and it just doesn’t make sense to convert to LED headlight bulbs.

For the doubting Thomases

Here’s a legal interpretation of the law from the legal counsel of the National Highway Traffic and Safety Administration:

Here’s the link if you want to verify this

Mr. Simon S. Shih

4 Teal

Irvine, CA, 92604

Dear Mr. Shih:

This responds to your e-mail, in which you seek clarification regarding the legality of high intensity discharge (HID) headlamp conversion sets, specifically whether it is legal to manufacture or sell sets of HID headlamps to replace original equipment halogen headlamp sets. We are pleased to have the opportunity to answer your questions related to Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices and Associated Equipment.

By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment. As a preliminary matter, we would clarify that we have no authority either to approve or disapprove motor vehicles or items of motor vehicle equipment. We do advise correspondents of the relationship of their products to applicable FMVSSs and other regulations that we administer. If a product is covered by one or more of our safety standards, its manufacturer must certify compliance of the product with all applicable FMVSSs prior to its importation or offering such product for sale. The symbol “DOT” on replacement lighting equipment is often mistaken for “DOT approval” of the equipment, but, in fact, it reflects the manufacturer’s own certification of compliance.

We believe that your questions are addressed by our March 13, 2003, letter of interpretation to Mr. Galen Chen (see enclosure). In that letter, we interpreted FMVSS No. 108 as requiring headlamps manufactured to replace original equipment headlamps to comply with all applicable photometry requirements using the replaceable light sources intended for use in the headlighting system on the vehicle for which the replacement headlamp is intended. Unlike other lamps, FMVSS No. 108 specifically regulates headlighting systems, including their light sources (see S7.1, S7.5, and S7.7). We adhered to this interpretation in a recent interpretation to Calcoast-ITL (69 FR 60464 (Oct. 8, 2004))(see enclosure).

Because replaceable light sources are, by regulation, designed to be non-interchangeable, it would not be possible for an HID headlamp conversion set to meet the standard’s photometry requirements for an original equipment headlamp system using a halogen light source, so the replacement lamps could not be sold for this purpose. Furthermore, a headlamp dealer or motor vehicle repair business could not remove the original halogen headlamps and install HID replacement headlamps without violating 49 U.S.C. 30122. That section prohibits manufacturers, distributors, dealers, and motor vehicle repair businesses from making inoperative equipment installed in accordance with a Federal motor vehicle safety standard. We cannot comment on the specific replacement lighting products that you mentioned because we do not have sufficient information on them.

Finally, in a subsequent e-mail, you asked whether our regulations require HID lighting systems to include “auto-leveling” and washing systems, similar to those incorporated in vehicles sold in Europe. The answer is no. FMVSS No. 108 does specify aimability performance requirements under paragraph S7.8 of the standard, but that paragraph does not require an “auto-leveling” capability. The standard also does not contain any requirement for a headlamp washing system.

It may be of interest to you, we also have enclosed a copy of our November 18, 2002, letter of interpretation to Mr. Jeff Deetz, which relates to kits that substitute the type of light source in existing headlamps.

I hope you find this information useful. If you have further questions, please feel free to contact Eric Stas of my staff at this address or by telephone at (202) 366-2992.


Jacqueline Glassman

Chief Counsel





© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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