The working principle of car headlights
The working principle of car headlights mainly involves three core links: light source emission, light control and beam adjustment.
The light source emits light
The mainstream light sources include halogen lamps, xenon lamps and LED lamps. Xenon lamps generate white strong light by stimulating gas discharge through high-voltage current, while LED lamps directly convert electrical energy into light energy through semiconductor materials, featuring energy conservation and long lifespan.
Light control
The combination of lenses and mirrors focuses or scatters the light emitted by the light source, forming an illumination beam that complies with regulatory requirements. For instance, low beam headlights should illuminate the road within 50 meters in front of the vehicle, and the illumination distance of high beam headlights should be greater than 100 meters.
Beam adjustment
Manual adjustment is achieved by controlling the motor to adjust the Angle through a sliding rheostat, while automatic adjustment relies on sensors to detect changes in ambient light or the dynamic balance of the vehicle in real time and drive the motor to fine-tune the beam position. Some models also support manual fine-tuning of the dashboard knob.
Car headlights are mainly used to provide road lighting for drivers at night or in low visibility conditions, while ensuring driving safety. Its core functions include:
Lighting function
The headlights should clearly identify obstacles within 100 meters ahead. The beam range of the high beams should be greater than 100 meters, and the beam range of the low beams should be approximately 50 meters to avoid dazzling oncoming vehicles.
Anti-glare requirements
When meeting oncoming vehicles at night, the lights should be tilted downward to illuminate the road 50 meters in front of the vehicle, reducing interference with the vision of other drivers.
When the headlight fault light of a car comes on, it is usually caused by the following reasons:
Common causes and handling suggestions
Youdaoplaceholder0 The bulb is broken
One or both side headlights may burn out due to long-term use or short circuit, and the original factory bulbs (recommended brands: Osram, Bosch) need to be replaced. Some models need to have their daytime running light groups replaced simultaneously.
Youdaoplaceholder0 Poor contact or short circuit
Check whether the headlight circuit is broken, worn or has poor contact, and repair or replace the damaged circuit. Animal gnawing or heavy rain corrosion may cause line faults, and it is necessary to focus on inspecting the roof lines.
Youdaoplaceholder0 the fuse blows
Check if the fuse of the headlight has blown and replace it with a suitable one (it is recommended to use a 25A-30A specification).
Youdaoplaceholder0 electronic control unit (ECU) failure
If self-inspection is ineffective, it might be an ECU fault. You need to contact a professional technician for inspection.
Emergency response
Restart the engine and observe whether the fault light goes out
Check whether the headlight switch is in the off position
Avoid driving at night and repair as soon as possible
If the faulty light remains on and is accompanied by abnormal lighting, it is recommended to contact a professional maintenance person for inspection.
When a car's headlight is damaged, the cause should be investigated based on the specific fault phenomenon. Common causes include burned bulbs, poor contact in the circuit, and blown fuses, etc. The following methods can be used to troubleshoot
Troubleshooting for bulb damage
If one side of the headlight does not light up, first check whether the bulb on that side is burned out. After removing the bulb, the resistance value can be tested with a multimeter (normal range: 55-65Ω). When replacing, it is recommended to use bulbs certified by the original factory (such as Osram, Bosch).
Handling of line issues
Poor contact or aging of the circuit can cause abnormal power supply. It is necessary to check whether the headlight plug is burned out and whether the circuit is broken. If the plug is found to be blackened, it needs to be replaced and make sure that the power of the new bulb matches that of the original car.
Fuse inspection
Open the fuse box in the engine compartment, find the fuse corresponding to the HEADLIGHT (usually marked as "headlight" or "Headlight"), and observe whether it has blown. If it blows, a new fuse of the same specification should be replaced.
Switch signal detection
If neither side of the headlights lights up, it is necessary to check whether the signals in the headlight control switch or the combined instrument are output normally. A voltage tester can be used to detect the current in the line to determine if the switch is damaged.
Youdaoplaceholder0 tip : When handling circuit operations, it is recommended to contact professional maintenance personnel to avoid potential safety hazards caused by self-handling.
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