Why is one rear fog light on and the other off?
2 Answers
The reason why one rear fog light is on and the other is off is that there is only one rear fog light. The main purpose of having only one rear fog light is to distinguish it from the brake light. Below are specific details about fog lights: Types: In addition to the front high beams, low beams, headlights, and parking lights, as well as the rear running lights and brake lights, most vehicles also have a set of anti-fog lights installed in inconspicuous locations at the rear. Rear fog lights are red signal lights installed at the rear of the vehicle to make it easier for other road users to detect the vehicle in low-visibility conditions such as fog, snow, rain, or dust. They emit a stronger light intensity than tail lights. Location: Fog lights are mounted at the front of the vehicle, slightly lower than the headlights, and are used to illuminate the road during rainy or foggy weather. Due to reduced visibility in foggy conditions, the driver's line of sight is limited. These lights can increase the visible distance, especially yellow anti-fog lights, which have strong light penetration and can improve visibility for both the driver and other road participants, allowing oncoming vehicles and pedestrians to spot each other from a greater distance.
Last week, my car's rear fog light had the same issue. While driving back to my hometown, I noticed the left one was on but the right one wasn't, almost causing an accident in the fog. At first, I thought the bulb had burned out, as it's normal for bulbs to fail when they reach the end of their lifespan—my car is almost ten years old, so the bulb was due for replacement. However, after checking, I found the bulb was fine, so it might have been a loose wire or a blown fuse. Aging circuits or poor contacts often cause one light to work while the other doesn't, especially with the rear fog light wiring, which is prone to corrosion. I opened the tailgate and checked the connector—sure enough, it was loose. Tightening it fixed the issue. If it had been a short circuit or blown fuse, I would have needed to use a multimeter to check the voltage, as unstable voltage can make the light flicker. If you can't fix it yourself, take it to a repair shop immediately—don't delay, safety comes first. Checking your car lights monthly can save you a lot of trouble and prevent driving nervously at night. Also, using fog lights more often in winter or rainy weather adds peace of mind.
