Why is only one reverse light on?

[StHadley]

The reason why only one reverse light is on is: it is permitted by national regulations. Vehicles with a length of less than 6 meters are required to have one mandatory reverse light, with an optional second one. Since national regulations mandate the installation of one reverse light, many manufacturers, while complying with the regulations, omit the second reverse light. The working principle of the reverse light is: when the car is in reverse gear, the mechanical mechanism presses down the switch contact, closing the circuit and turning on the reverse light. When the reverse gear is disengaged, the switch contact springs back, the reverse light circuit opens, and the reverse light turns off. Precautions for reversing include: 1. Adjust the interior rearview mirror properly; 2. Pay attention to both side mirrors; 3. Control the speed; 4. Stop and wait if there are pedestrians or oncoming vehicles; 5. Use the reverse camera to judge the accurate distance.

[LaKatherine]

My car recently had the issue of only one reverse light working, which really worried me. The mechanic told me it’s actually very common, and 80% of the time it’s just a burnt-out bulb. Think about it—reverse lights operate in a high-temperature exhaust environment all the time, so they age particularly fast. If the tungsten filament breaks, you just need to replace the bulb, which costs around 30 yuan. But if it’s not the bulb, the problem gets trickier—it could be corroded wiring causing poor contact, a blown fuse, or even rust on the reverse light bracket leading to looseness. Later, I touched the light cover and noticed the non-working side wasn’t warm at all, confirming it was a power supply issue. The mechanic used a multimeter and found it was indeed a blown fuse. In such cases, never try to rewire it yourself—short circuits can be dangerous. Driving with only one reverse light is especially risky, particularly at night when it’s hard to see curbs or obstacles. I recommend getting it checked at a professional shop as soon as you notice the problem.

[Athena]

My friend's new car, only driven for two years, was found to have only the right reverse light working. At first, we thought it might be designed that way by the manufacturer, but checking the manual revealed it should have both lights on. There are typically three common possibilities for such a fault: the most likely is a burnt-out bulb, given the frequent on-off usage during reversing; secondly, water ingress into the lamp socket causing a short circuit; or possibly a break in the power supply line. I accompanied him to the repair shop, where the technician removed the trunk interior panel to inspect and found that the socket's spring contact was deformed and the contact point had oxidized, preventing conductivity. Nowadays, many cars have their reverse light wiring hidden behind sealed rubber strips, making it impossible to see on your own. With only one light working during reversing, the shadowed area makes it really hard to see objects behind, especially low obstacles like curbstones or children. The technician also reminded us that if bulbs burn out frequently, the generator's voltage should be checked, as excessive voltage can accelerate bulb failure. Now, he takes the opportunity during monthly car washes to routinely check the lighting conditions.

[LaLilah]

I've encountered the single-side reversing light issue twice. The first time, replacing the bulb fixed it, but the second time, a new bulb still didn't work. Later, I found out it was due to a blown 15A reversing light fuse in the fuse box. It's advisable to first check the vehicle manual to confirm if dual reversing lights are standard, to avoid misdiagnosis. Common failure points include bulbs and fuses, as well as wiring harness wear or breakage (especially near the trunk hinges), control module faults, and loose connectors. During the last repair, a new issue was discovered: short circuits caused by improper wiring from an aftermarket reversing camera installation. Repair shops typically perform circuit continuity tests, checking fuses first and then verifying if the supply voltage is normal. Having only half the reversing light brightness at night is dangerous, so I've added temporary auxiliary lights to the rear window as an emergency measure.