What are the reasons for both high and low beams not working?

[MacHenry]

The reasons for both high and low beams not working are: first, the headlight bulb may be burnt out - simply replace it with a new one. Second, the fuse for the right headlight bulb may be blown (fuses are prone to burning out). Third, the headlight wiring may be disconnected, preventing power from reaching the bulb. It is recommended to first check the bulb and fuse. Definition of automotive headlights: Automotive headlights, also known as car front lights or LED daytime running lights, serve as the "eyes" of a vehicle. They not only relate to the external image of a car owner but are also closely tied to safe driving at night or under poor weather conditions. The use and maintenance of car lights should not be overlooked. Precautions for using headlights: With the increasing number of vehicles on the road, the quality of drivers varies greatly. When encountering inconsiderate drivers, try to use headlights and horns reasonably to send appropriate "warning" signals. Avoid adopting a "tit-for-tat" approach. Experienced drivers often advise against driving out of anger, as road safety should always be the top priority.

[LaRonan]

I often help friends with such issues. When both the high and low beams don't work, it's usually due to a shared power supply problem. First, check the fuse because high and low beams typically share the same fuse—if it's blown, both lights will lose power. The cause could be a short circuit or current overload, such as improper modifications or aging wiring. Secondly, a faulty relay can also interrupt power supply. I've seen many cases where the lights suddenly fail while driving, requiring testing of the relay contacts or replacement. Additionally, wear and tear on the headlight combination switch is common, especially in older cars. Poor internal contact in the switch can prevent signal transmission. For newer cars, check the voltage regulator—unstable alternator voltage might damage the entire system. In short, driving without headlights is dangerous. Don't risk driving at night; take the car directly to a repair shop for professional diagnosis, and it can be fixed quickly. Regular maintenance with attention to wiring checks can prevent sudden breakdowns.

[VonNathan]

As someone who has driven for many years, I'm particularly alert to headlights not working. When both high and low beams fail to illuminate, it indicates more than just a burnt-out bulb—it's likely an entire circuit issue, possibly a blown fuse or a faulty main switch. Common root causes include: the fuse protection function activating due to a short circuit or overload, interrupting the current; or aging relay contacts failing to activate the headlight circuit; or issues with the vehicle's electrical system, such as a faulty alternator causing voltage that's too high or too low, affecting power supply. In such cases, immediately turn on the hazard lights and pull over to avoid accidents. Try to locate the fuse box yourself—usually, the manual has a diagram—but avoid tampering to prevent damage. Safety first; promptly schedule an inspection at a 4S shop where they can quickly diagnose and fix the issue. Regularly clean lamp sockets and wiring to reduce the risk of malfunctions.

[LeAndrew]

My car had the same issue—suddenly all the lights went out while driving at night, which was quite a scare. The usual culprit is a blown fuse, since high and low beams share one fuse, and a short circuit or overload can cause both to fail simultaneously. Alternatively, it could be a faulty headlight switch with poor contact disrupting the signal. I tried replacing the fuse myself—just check the manual for the correct model, but remember to disconnect the power first for safety. If the fuse is fine, the relay might be the problem. Voltage instability, like abnormal alternator output, can also trigger this. Simple maintenance: inspect the fuse box monthly and clean any oxidized connectors. If you're not familiar with circuits, don't force DIY repairs—getting a professional mechanic to handle it is much faster.