Why is one rear fog light on while the other is off?

[LaKyle]

It is normal for one rear fog light to be on while the other is off. Reason for having one rear fog light: While low beam headlights and brake lights come in pairs, rear fog lights are designed with only one. According to European Union regulations, if two rear fog lights were installed and positioned more than 10 cm apart from the brake lights, they could easily be confused with position lights or brake lights. Therefore, rear fog lights are designed as a single unit and emit red light. Usage of fog lights: Fog lights are essential for illuminating the road ahead and ensuring driving safety under adverse weather conditions such as fog, snow, heavy rain, or in environments filled with smoke or dust. In recent years, fog lights have commonly been integrated into the design of the front bumper.

[Paul]

I've seen this situation quite often—it's likely the rear fog light bulb has burned out. Rear fog lights are designed to enhance visibility in foggy or adverse weather conditions, helping to prevent rear-end collisions. The most common reason for one not working is simply that the bulb has reached the end of its lifespan or the filament has broken. Another possibility is a blown fuse—especially if that light has its own dedicated fuse. Wiring issues such as loose connections or short circuits can also interrupt the current flow. I recommend starting with a simple self-check: open the rear cover to inspect if the bulb is burnt out and try replacing it with a new one. If it still doesn't light up after replacement, check the corresponding fuse in the fuse box to see if it's blown. Wiring damage usually requires professional tools for diagnosis. Don't underestimate this issue—insufficient rear lighting in foggy conditions increases accident risks. Remember to periodically check your vehicle's lighting status; incorporating this into routine maintenance can prevent problems.

[DeAmir]

My car had the same issue last month—the left fog light worked fine, but the right one just wouldn’t turn on. Took it to the repair shop, and turns out the bulb was burnt out. Replacing it yourself isn’t hard: just remove the lamp cover, take out the old bulb, and put in a new one to test. If it’s not the bulb, the mechanic said you’d need to check the fuse, wiring connections, and switch. The rear fog light’s key role is providing extra illumination, especially in heavy rain or fog when others might struggle to see your car’s rear. While one light out isn’t a major issue, ignoring it for too long could lead to more serious wiring faults. My friend’s car nearly caught fire because of a similar issue causing overheating in the wiring. So, if you notice it, get it fixed right away—don’t delay. After the repair, all lights are working now, and driving feels much safer. Making a habit of a quick monthly check on your car lights can save a lot of hassle.

[DiLouis]

It's quite dangerous when one rear fog light is working while the other isn't. These lights primarily protect you in low visibility conditions by preventing rear-end collisions. A single malfunctioning light can make it difficult for following vehicles to judge distance and position. The usual causes are a burnt-out bulb or oxidation on the lamp socket leading to poor contact. It could also be a blown fuse or a short circuit in the wiring. When I discovered this issue, I addressed it immediately: first by replacing the bulb for testing, and if that didn't work, checking the fuse and connections. Don't hesitate—safety comes first. The risk increases significantly in foggy conditions with one less light. Promptly visiting a repair shop or fixing it yourself can reduce the risk.