Driving without your high beams (AKA the brights) isn’t exactly a bright idea especially on rural roads. If the high beams aren’t working on your car, you may want to slow down at night when the road gets winding, so you don’t strike any unseen obstacles. To drive with confidence again no matter how dark the road gets, get your high beams working. So here we’ve compiled 6 of the most-common causes why headlights don’t work.
Blown Headlight Bulb
This is the most common cause of a single high beam headlight not working, but isn’t common if both high beams aren’t working, because it’s highly unlikely that both bulbs would blow at the same time. Headlight bulbs have a limited lifespan (450 to 1,000 hours) so they’ll eventually burn out.
Blown High Beam Fuse
A fuse protects the wiring from damage, in case too much current is being drawn through the high beam circuit. The fuse will blow if there’s a short circuit, but it might also blow if an accessory is drawing off it or if the bulb is the incorrect wattage
Failing HID Generator
In the case of high-intensity discharge (HID) headlights, or Xenon headlights, there’s an additional component. To get the xenon and salts to plasma state, the HID generator bumps the voltage up to 30,000 V, then stabilizes around 90 V when the bulb is in operation. If the generator fails, the bulb won’t light.
Broken wiring simply stops current flow, while chafed or damaged wiring might send it elsewhere, to ground or to another circuit. Loose or corroded connections, especially at the headlight bulb, can overheat and melt.
If the high beams function but don’t seem to light your way, especially if you drive an older vehicle with polycarbonate headlight lenses, your car may be a victim of headlight fogging. This isn’t simply scuffing, but an actual chemical change from polycarbonate’s exposure to solar ultraviolet light and caustic exhaust emissions. The diffused light doesn’t project very well, making it hard to see, even when your high beams are on.
Incorrect Headlight Bulb
On some vehicles, particularly those with HID headlights or solid-state circuit protection (Zener diodes or high beam circuit breakers) installing the wrong bulb might result in intermittent headlight operation or no high beams at all. The wrong bulb might not ignite at the right voltage or draw too much current for the circuit protection’s design.
Headlight bulbs are available in every auto parts store, so it should be easy to find what you need. Check your owner’s manual to be sure which kind of high beam bulb you need and get familiar with the fuse box in case the high beams stop working. Finally, practice using a digital multimeter so you can rule out electrical problems before replacing other components.