What are the reasons for both high and low beams of car headlights not working?
3 Answers
Car headlights not working for both high and low beams may be due to a blown fuse or burnt-out bulbs. Here are the specific reasons: Check if the fuse is blown: If all lights are on, it indicates a failure in the dimmer switch. If the high beams are not working, check if the high beam indicator is on. If it is, the fault lies between the terminal block and the headlights. If not, the issue is between the terminal block and the dimmer switch. If only one headlight is working while the other is not, it could be due to a burnt-out filament, an open circuit in the wiring, or poor grounding (dim headlights). Burnt-out bulbs: The voltage regulator may be faulty, causing excessive voltage. Poor contact in the battery cables can lead to excessive no-load voltage from the generator. There may be a short circuit between the generator's armature and field coils.
Ah, I recently encountered this issue too, the entire headlight going completely dark is really scary. The most likely cause is the fuse blowing together, those long strips in the little black box under the hood or near the steering wheel. Another big suspect is the headlight switch assembly; worn or aged copper contacts inside can cause both high and low beams to fail simultaneously. The possibility of a short circuit in the wiring can't be ignored either, especially after driving through puddles on rainy days—I’ve personally seen a fellow car enthusiast’s wiring harness insulation crack, causing wires to stick together. Rusty grounding wires are also common; last time I helped my cousin fix his decade-old Japanese car, peeling back the wiring harness connector on the side of the engine bay revealed nothing but green rust. If none of these are the issue, then you might suspect the headlight relay—just because you hear the clicking sound doesn’t mean it’s still conducting electricity. Remember to turn on your hazard lights first before pulling over, folks!
Buddy, your situation basically falls into one of these four common issues. For fuses, you need to check both the main power supply fuse and the dedicated headlight fuse positions—it's like when both the main circuit breaker and light switch trip simultaneously in a house. A faulty combination switch is the most troublesome; my American car's left steering column lever got stuck, and replacing the whole set cost me 600 bucks. Wiring shorts are the most dangerous—just last week, a car club member shared photos showing engine bay wiring harnesses chewed by rats, exposing copper wires. Poor grounding is also common; I remember seeing three out of five cars at the repair shop having their chassis grounding points sanded down last time. A pro tip: keeping spare fuses in the glove box is super handy—in emergencies, you can even use the cigarette lighter fuse removed with nail clippers as a temporary replacement.
