If your car has a headlight that puts out about as much light as a flashlight with weak batteries, we’ve got two simple fixes for you.
Most DIYers think they’ve got a bad headlight switch or a bad connection in the power feed. But most dim headlights are caused by a corroded ground wire. Just trace the wiring harness from the back of each headlight assembly and see where it connects to the vehicle body. Clean it as described in the photo.
Another possibility is that as headlight filaments age, they deposit a gray/brown film on the inside of the bulb (See Photo). Over time, that coating can reduce visibility by almost 300 ft. If your headlights aren’t as bright as they used to be, yank one of the bulbs and look for gray or brown residue on the glass. If you find any, replace both bulbs now and get back to seeing more of the road.