What are the reasons for both high and low beams of car headlights not working?
2 Answers
The reasons for both high and low beams of car headlights not working may be a blown fuse or burnt-out bulb. Below are some precautions regarding car headlight maintenance: 1. Maintain sealing: Moisture intrusion can reduce the lifespan of the bulb, so it is important to check the sealing of the headlights. 2. Keep clean: Clean the reflector; if the reflector of a semi-sealed headlight turns black and the light intensity decreases, it should be replaced. If the reflector is silver-plated or aluminum-plated, due to its lower hardness, only clean cotton soaked in hot water should be used for cleaning, and never wipe it to avoid damaging the reflector coating. Clean the bulb: When there is dust or dirt on a halogen bulb, use degreasing cotton soaked in ethanol (90%) to wipe it.
I've driven trucks for half my life on long-haul routes and seen plenty of cases where both high and low beams fail. The most common culprit is a blown fuse—it acts like a guardian angel, sacrificing itself to cut off power when the current gets too high, preventing damage to other components. Another possibility is a faulty combination switch; poor contact when turning the handle can interrupt the signal. The bulb itself might also be dead, especially with H4-type dual-filament bulbs where one filament breaking takes the other down with it. Aging or short-circuited wiring is another risk, like loose connections from engine vibration. When this happens, I first check the fuse box under the hood and replace the corresponding fuse—that usually fixes it. Otherwise, I head straight to a professional repair shop since driving at night without lights is like feeling your way in the dark—way too risky. Regular headlight checks can save a lot of hassle.
