Can you retrofit LED bulbs into a halogen headlight?
Here’s why you should never retrofit LED bulbs into a halogen headlight
Quick Summary
You should never retrofit LED headlights into any halogen headlight assembly. Here’s why:
• Retrofitting LED headlights is illegal
• It’s optically impossible for a retrofit LED bulb to produce the proper beam pattern when placed into a reflector or projector-style headlight designed for a halogen bulb.
• Retrofit LED bulbs produce severe glare when used in a headlight designed for a halogen bulb, and cannot meet Federal Motor Vehicle Safety Standard (FMVSS) 108. The physics of halogen optics make it impossible for retrofit LED headlights to produce a correct beam pattern—whether in a reflector housing or a projector housing.
• Due to the
e physics, retrofit LED bulbs cast less light on the road
Article
Many “Tik Tok experts” state that LED bulbs work just fine in a projector headlight. They don’t. They can’t because you’re asking the projector headlight to defy the laws of physics. Scroll down to learn why it’s optically impossible for an LED retrofit to produce the proper beam pattern when installed in a halogen projector headlight assembly
The blue light from LED retrofit bulbs produces more glare
• Traditional halogen bulbs produce light at around 3,000° Kelvin; towards the red end of the spectrum. But LED bulbs produce light in the 5,000 to 6,000° K spectrum.
Blue light has shorter wavelengths (450 to 495 nanometers) and higher frequencies, causing air particles to oscillate faster and scatter more in the atmosphere than other colors. This applies to ALL blue light sources, whether LED or HID.
That’s why the headlight assembly must be explicitly designed for the bulb type. Putting an LED bulb into a halogen headlight assembly produces more glare and the blue color reduces driver visibility.
Retrofit LED headlight bulbs will never match the beam pattern, even in a projector headlight, and you can’t aim an LED headlight bulb to work in a projector headlight.
There isn’t a single LED retrofit bulb sold anywhere that’s street-legal to replace a halogen bulb
There isn’t a single LED or HID retrofit that contains a D.O.T. marking. Most retrofit bulbs say they’re “for off-road use only,” or they don’t say anything on the package.
Why retrofit LED can’t produce the proper beam pattern
The LED light source is totally different from a filament bulb, and that prevents the headlight from producing the proper beam pattern
• Halogen bulbs have a single filament light source that’s cylindrical and casts light in a 360° pattern. The reflector and lenses inthe reflector and projector headlight are designed to reflect and focus the light from this light source properly
• LED bulbs have two flat light sources that only cast light in 270°, so when they’re used in a reflector or project headlight, there will be 90° of dead spots.
Because halogen headlights aren’t designed for two flat light sources, they can’t produce the proper beam pattern. Here’s what happens when you install LED bulbs in a halogen headlight assembly:
• Because the reflector and lens are designed for halogen bulbs, they produce GLARE and BLINDING when fitted with LED bulbs
• LED bulbs in a halogen headlight produce more light scatter and actually throw less light on the road, and produce the wrong beam pattern.
How a projector headlight works
The reflector focuses the light to a “hot spot” located at a midway point between the reflector and the lens. The lens then projects this hot spot onto the road.
Change the bulb and the beam no longer focuses midway between the reflector and the lens. So less light gets refocused on the road and since the focus is off, more light ends up as glare.
Why LED headlight retrofits don’t work in projector headlights
First, the LED light source isn’t a 360° sphere, so it can’t properly reflect to the midpoint. Second, since the reflector in a projector headlight (yes, they have reflectors) is designed for a halogen bulb, and LED bulbs don’t match the focal length, size, and shape of a tungsten filament, the reflector it can’t place the hot spot in the pre-determined midway point between the reflector and the lens. The lens will project less light on the road and produce more glare into oncoming traffic simply because the light is in the wrong place inside the headlight.
©, 2021 Rick Muscoplat