most headlight systems are straightforward and include a few basic components like the bulbs, a relay, a fuse, and a switch. there are variations on this basic theme, like some vehicles have daytime running lights, adaptive headlights, or other little wrinkles like fog lights, but the idea is still the same. when you turn on your headlights, that switch activates a relay. that relay, in turn, actually provides the electrical connection between your headlight bulbs and the battery. fuses are also involved in order to provide a sacrificial failure point to protect the rest of the wiring.
if any of these components stop working properly, your headlights will fail. and by looking at the way they failed, you can usually backtrack to figure out the best place to start troubleshooting.
when headlights stop working, it’s either an electrical problem or a physical issue with the bulbs themselves. in order to get to the bottom of the situation as quickly as possible, it’s important to make note of exactly what type of failure you have experienced. based on which bulbs have stopped working, and under what circumstances, you can use the following information to narrow down a solution:
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one headlight doesn’t work
this is usually caused by a burned out bulb. you can replace the bulb. if it still doesn’t work, suspect a wiring or fuse problem.
neither of the headlights work
it’s safe to say this is cause by either burned out bulbs, or an issue with power or ground. check for power and ground, and fix if necessary. otherwise, replace the bulbs. bulbs usually don’t burn out together, but it’s still important to rule that out by checking for power. most total headlight failures are caused by a bad component like a fuse, relay, or module. wiring problems can also cause both headlights to stop working.
high beam headlights don’t work or low beams don’t work
a burned out bulb, or a problem with the high beam switch or relay can be the culprit here. you’ll need to replace the bulb, switch, or relay. if just one bulb fails to work in either high beam mode or low beam mode, it may be the bulb. most headlight failures that are limited to just high or low beams are related to a relay or the high beam control switch.
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headlights work but seem dim
this could be an issue with foggy lenses, worn out bulbs, or a charging system issue. clean the lenses, replace the bulbs, or repair the charging system. if your headlights always seem dim, the problem could be foggy lenses or worn out bulbs. if your headlights seem to dim during specific circumstances, there may be a charging system issue.
fixing a burned-out headlight is usually an easy
work, but there are cases where you may want to bring your car straight to state street auto repair. if you don’t own some basic tools and diagnostic equipment, like screwdrivers and a voltmeter, then you may want to think about bringing your car to a professional. we are here to help answer all your headlight questions and make sure your headlights are working properly, shining brightly, and keeping you safe!
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