Whether you’re driving at night, in the rain, in the fog or snow, having working headlights is absolutely vital. They light is provided so you can see where you’re going, but they also help alert other drivers to your coming, enhancing the safety of everyone you meet on the road. If your headlights seem dim, there may actually be an underlying problem that needs to be corrected.
How the headlight system works:
No matter what type of bulbs you’re using, the system operates in the same basic way. Your headlights are connected to the engine wiring harness through connectors, and they’re grounded to the chassis of your car (without a ground, they won’t function).
When you turn on the headlight switch, power is transferred from the battery/alternator to the bulbs, causing the filaments to heat up and glow, which gives off the light you need to see the road. They work just like the light bulbs in your home – a broken filament, or anything that disrupts the flow of electricity through the circuit can create problems.
However, bulbs are a lot like fuses in that they either operate or they don’t work. That means if your bulbs are dimmer than normal, the problem isn’t likely in the bulb itself, but somewhere in the wiring leading to the bulbs.
Common reasons for this problem:
- Corroded Ground Wire: One of the most common reasons for having a dim headlight is a corroded ground wire. Ground wires connect the bulb circuit to your vehicle’s chassis (which serves as the ground itself). If corrosion starts on the wire (or the connection is dirty or damaged), it disrupts the flow of electricity, often enough to reduces the output of your bulbs.
- Discoloring Deposits: This is mostly common with halogen type light bulbs. Over time, the inert gas within the halogen bulb creates a discoloring film (brown or gray). This builds up on the inside of the bulb and dims the light output. changing the bulb is generally the only option here.
- Bad Alternator: Another very common reason to see dim headlights is a bad alternator. If you notice that the lights brighten and dim as the engine revs up and down, the alternator should be inspected immediately. If it fails, dim lights will be the least of your problems. The car will start pulling power from the battery and because it’s not being recharged, it will eventually drain completely. This will leave you stuck on the side of the road.
- Yellowed Lenses: most times, dim lights have nothing to do with the flow of electricity or aging bulbs. Rather, they have to do with the aging of the headlight lens (the large plastic cover that protects the bulbs inside). Lenses yellow as they age, and this influences the amount of light that can escape and limits your visibility at night.
- Loose Alternator Belt: Dimming lights may not be a sign of a bad alternator. It might be a loose alternator belt rather. If the alternator belt is loose, it doesn’t turn the pulley properly (it slips and then grabs, slips and then grabs). This can be noticed in dimming and brightening headlights. The belt should be inspected for excess play, as well as wear and tear.
How it’s done:
The mechanic will check all parts of the headlight system, including the lenses, the bulbs, the wiring connectors, the ground wires and more. It may be necessary to carry out a charging system test to determine if your alternator is healthy. The mechanic may also need to check the alternator belt.
How important is this repairs?
If your headlights are dim, it could be a sign of a serious underlying issue. Even if the issue is something as simple as a corroded ground wire, your safety is still compromised because you don’t have adequate visibility at night and while driving in inclement weather.