What is the principle behind the function of the rear fog lights in a car
The main function of the rear fog lights of a car is to enhance the visibility of the vehicle through high-brightness red light sources in low-visibility environments such as rain, fog, snow or dust, enabling other road traffic participants behind to spot the vehicle in time and thereby reducing the risk of rear-end collisions and other accidents.
Its working principle is based on the physical properties of light and optical design. Rear fog lamps usually use red light sources because red light has a longer wavelength and a stronger ability to penetrate fog, dust and other media, effectively reducing light scattering.
Inside the lamp, the light is focused and projected in a specific direction through mirrors, forming a wide horizontal beam of light, ensuring visibility from 100 meters away.
Meanwhile, the brightness of the rear fog lights is much higher than that of ordinary taillights (usually more than three times), meeting safety regulations to ensure the warning effect.
The installation position of the rear fog lights is usually located at a lower part of the rear of the vehicle (such as near the bumper). This design enables the light to shine on the ground at an appropriate Angle, avoiding the scattering of light in the fog due to being too high and thus becoming ineffective.
In terms of operation, the rear fog lights can only be activated after the side marker lights or low beam lights are turned on to prevent misuse.
Rear fog lamp malfunctions are usually caused by blown fuses, damaged bulbs, wiring issues or switch failures, and can be gradually investigated and resolved.
Self-inspection steps
Youdaoplaceholder0 Check the fuse : Open the fuse box, find the fuse corresponding to the rear fog lamp. If it has blown, replace it with a fuse of the same specification.
Youdaoplaceholder0 Replace the bulb : After disassembling the fog lamp bulb, observe whether the filament is broken or the glass is black. If there is any damage, replace it with a matching new bulb.
Youdaoplaceholder0 Check the wiring connection : Make sure the fog lamp plug is firmly connected to the socket, and check if there is any damage, short circuit or poor contact in the wiring.
Youdaoplaceholder0 Test the fog light switch : Operate the fog light switch and observe whether the indicator lights on the instrument panel are on. If it doesn't light up, it might be a switch fault that needs to be repaired.
Situations requiring professional maintenance
If the above steps are ineffective, it may be due to a fault in the control module or a complex circuit issue. It is recommended to go to a professional repair shop for inspection.
Is it normal for only one rear fog lamp to be on
It's actually quite common for only one of the rear fog lights to come on. Most cars are only equipped with one rear fog lamp, usually on the left side. This design complies with regulations and safety requirements.
Regulations permit a single-side rear fog lamp design
According to the "GB4755 Regulations on the Installation of Lighting and Light Signal Devices for Motor Vehicles and Trailers", a vehicle must have at least one rear fog lamp. If two are to be placed, they must be placed symmetrically. If only one is installed, it must be placed on the left side of the driving direction. This regulation is made to prevent confusion between the fog lights on both sides and the brake lights, reduce the risk of rear-end collisions, and also minimize visual interference to the vehicles behind.
Some models only have rear fog lights on the left side
Many economy cars and some joint venture cars adopt the "left fog, right reverse" design, with red rear fog lights on the left and white reverse lights on the right. This design not only complies with regulations but also optimizes the space of the taillights. It uses asymmetrical light sources to enhance the warning effect and prevent drivers from feeling numb to symmetrical light.
If a car was originally designed with dual rear fog lights but only one is actually on, it might be that the bulb is broken, the fuse is blown, or the circuit contact is poor. At this point, it is necessary to check whether the bulb is blackened or the filament is broken, whether the fuse is blown, whether the plug is loose or the circuit is damaged. If necessary, replace the parts or go to a professional repair point for inspection.
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