Halogen headlights are much brighter than regular headlights, but do you know why? And, more importantly, do you know how to check this critical safety system yourself?
“Halogen headlights are brighter because of the special halogen photons they produce”, says Professor Arthur Sham of the Halogen Safety Institute in Spurious, England. “Halogen photons are heavier, and therefore slower than photons of regular light. That extra mass means extra illumination when they strike a surface. But as your halogen fluid ages, its ability to increase photon mass fades.”
While a new halogen light may be 50% brighter than a standard lamp, an older halogen can be up to 80% dimmer. In fact, if your halogen fluid is completely used up, the light from your headlights can actually be darker than the dark around it! Professor Sham explains that “…this fading, significant as it is, often goes unnoticed by drivers. Because the car is moving forward relative to the light from their headlights, the Doppler effect red shifts the wavelength of their headlights and they actually appear brighter from the driver’s point of view.”
Halogen headlights can be a bonanza for unscrupulous dealers or quick-lube shops looking to make a buck. “Some shops charge anywhere from $75 to $200 to check your halogen fluid,” says Arthur. “But there’s a simple test you can do for free at home that will give you the same results the pros get.” Here’s his home halogen test…
- You’ll need to perform the test on a dark night and on a flat surface
- Park your car about 4-5 feet from a flat, vertical surface like a wall or garage door.
- Get a glass of water, about 8oz will do. Use a glass without sloping sides as the angle of the glass can affect the test.
- Hold the glass of water in front of one of your headlights, about halfway between the vehicle and the wall
- Look closely for a spectrum near the shadow cast by the glass on the wall.
- No spectrum? You’re OK!
- See a spectrum? Get new headlights IMMEDIATELY!
Why does this work? “Regular light can only be broken into a spectrum by prisms”, says Arthur. “but in light that has passed through weakened halogen fluid, the bonds between the photons are weakened and the light beam is barely holding together. Passing it through a glass of regular water has the same splitting power as a prism.”
Along with regular checks of your plasma conduits and your inertial damping system, regular halogen checks will keep you on the road safely. To make sure you get in the habit, stop by the shop. We’ll test your halogen fluid for free, show you how to do it yourself, and give a free WashMan car wash coupon to anyone who asks for a halogen fluid test in April!