The function of car headlights
The headlights of a car mainly provide road lighting at night or in low visibility conditions, ensuring that drivers can clearly identify obstacles within 100 meters ahead. They are also equipped with anti-glare devices to prevent interference with other vehicles.
Lighting function
The front headlights must meet the illumination distance requirements: the illumination distance of high beams should be greater than 100 meters, and that of low beams about 50 meters. Moreover, they need to illuminate the entire road section and avoid deviation.
Anti-glare requirements
Equipped with anti-glare devices to prevent visual interference to oncoming drivers when meeting oncoming vehicles at night.
Light adjustment function
Some models are equipped with an automatic adjustment system that can automatically adjust the irradiation Angle and brightness according to the external environment, such as automatic opening and closing, steering following, etc.
The working principle of car headlights mainly falls into two types: traditional bulb light emission and gas discharge light emission. The following is the specific explanation:
The principle of light emission of traditional light bulbs
The front headlights generate light by heating the filament to incandescence through an electric current. In the early days, tungsten filament lamps (such as incandescent lamps and halogen tungsten lamps) were mostly used. This type of lamp structure consists of a filament, a reflector and a light distribution mirror. The light is projected directionally through the reflector to ensure the lighting effect at night.
The principle of gas discharge luminescence
Modern car models mostly adopt xenon headlights. The principle is that high-voltage current excites the xenon molecules in the quartz tube to ionize and emit light, generating a white, high-color-temperature light source similar to sunlight. This type of light source has higher brightness and a wider illumination range, but its structure is relatively complex and needs to be combined with a booster to instantaneously increase the low-voltage current of the vehicle to a high-voltage current.
Both technologies require the optimization of light pattern distribution through optical components such as mirrors and light distribution lenses to ensure driving safety at night.
Car headlight malfunctions may be caused by damaged bulbs, wiring issues or abnormal power supply. The following steps can be taken to troubleshoot
Common causes of faults
Youdaoplaceholder0 bulbs burned out (accounting for 38%)
It is manifested as a decrease in the lighting intensity on one or both sides, but the fuse has not blown. A multimeter should be used to test the resistance of the bulb (normal value: 55-65Ω), and the bulb should be replaced with an original factory-certified one (recommended brands: Osram, Bosch). Some models need to have their daytime running light groups replaced simultaneously.
Poor contact or short circuit of line (accounting for 29%)
The line runs through the roof of the vehicle, making it vulnerable to being gnawed by animals or corroded by heavy rain. It is necessary to check whether the plug is burnt or loose. Replace the wiring harness if necessary. If there is an abnormal noise, it may be due to a short circuit in the circuit or a relay fault. The relay needs to be replaced or the connection of the circuit should be checked.
Youdaoplaceholder0 power supply system abnormality
A malfunction of the generator regulator or unstable battery voltage may cause unstable power supply. It is necessary to check whether the power generation is normal and repair the voltage stabilizing system if necessary.
Solution
Youdaoplaceholder0 check by itself:
Check if the bulb is burned out (observe if the filament is broken).
Check if the plug is loose or oxidized (sand the contact points with sandpaper).
Test the continuity of the circuit (use a test lamp to detect the connection of the live wire of the switch to the post).
Youdaoplaceholder0 professional repair :
If you fail to check by yourself, it is recommended that you go to a 4S store to have the relay, short circuit or grounding problem checked.
Precautions
When replacing light bulbs, choose the original factory or certified brand (to avoid false power labeling), and avoid using bulbs with a power higher than that of the original factory.
If there are foreign objects or cracks inside the headlights, they should be replaced in time to prevent moisture from seeping in and affecting their lifespan.
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