Why is the replaced car headlight cover not as bright as before?
4 Answers
Reasons why the replaced car headlight cover is not as bright as before are as follows: Bulb malfunction: If you have a spare bulb, simply replace it. If there is no bulb to replace, such as when the low beam bulb is damaged, you can use the high beam to drive, but this will cause a lot of trouble for oncoming vehicles. Fuse blown: Check the relevant fuse. If the fuse is indeed blown, simply replace it with a fuse of the same capacity. Poor contact in the power socket: Walk to the front of the car and tap the non-functioning headlight cover with your hand. If the headlight lights up momentarily, it can be confirmed that the socket contact is poor. In this case, simply unplug the headlight power socket and plug it back in.
I think the most common issue with newly replaced lamp covers not being bright enough is the quality of the parts. I once helped my brother replace his with an aftermarket cover, and the plastic was noticeably dull—light passing through it looked like it was filtered through frosted glass. OEM covers use polycarbonate with UV coating, while cheaper aftermarket ones use ordinary plastic that yellows after just six months in the sun and fogs up in rainy weather. Poorly applied sealant can also let in dust and moisture, causing even more light scatter. If the installer isn’t careful—like leaving fingerprints or sweat marks on the inner surface—those marks might not be visible during the day, but at night, they turn into glaring light spots. My advice? Go to a reputable shop and use certified parts—the lifespan of the cover can differ by more than double.
Last time, the repair shop owner told me that insufficient brightness of new lamp covers is often related to installation. When replacing the lamp cover, the headlight assembly needs to be disassembled. Many small shops rush the job, applying sealant unevenly, leading to dust accumulation within six months. Moisture condenses into white fog inside the cover, reducing light transmission by 30%. Additionally, old reflector bowls can fade and discolor over years of use, making them appear dimmer when paired with a new lamp cover. My neighbor fell victim to this and ended up paying out of pocket to replace the entire headlight assembly to fix the issue. It's recommended to have the technician thoroughly clean the internal reflector when replacing the lamp cover. If the old parts are severely oxidized, replacing the entire assembly is more cost-effective.
The headlight cover becomes dimmer after replacement often due to poor maintenance. In the past, I didn’t pay attention after replacing my car’s headlight cover, and after just two highway trips, it was covered in bug remains. During car washes, I only rinsed the surface casually, allowing oil film to accumulate thicker on the inside. Professional shops use headlight restoration polish to wipe the covers, which dissolves resin and enhances transparency. Some people leave their newly replaced covers exposed to direct sunlight, accelerating plastic aging due to UV rays—original parts can last five years, but careless handling turns them yellow in just two. It’s best to check the cleanliness of the cover monthly and park in shaded areas. If you really want to save money, buy UV coating spray from Taobao and maintain it yourself to delay yellowing.
