Symptoms of a Bad or Failing Headlight Bulb

Headlights are some of the most important lights found on road going vehicles. They provide the illumination that helps the driver both see, and be seen when driving on the road. The light is provided by high intensity bulbs that are installed in plastic or glass headlight housings. Headlight bulbs can come in a wide variety of shapes, sizes, and designs, and are designed to be replaceable when they burn out. As the lights provide illumination for low light conditions, they are very important to the overall safety and drivability of the vehicle, especially for night time driving. When the headlight bulbs fail, the vehicle can be left without the very important safety and visibility that is provided by the headlights. Usually faulty headlights will produce a few symptoms that can let the driver know that they may require attention.

1. Dim headlights

One of the first symptoms of a bad or failing headlight bulb is dim headlights. Over time headlight bulbs can wear out and begin to shine noticeably dimmer than when they were new. A dim headlight will not provide proper illumination and is also usually a sign that the bulb is approaching the end of its service life.

2. Headlights flickering on and off

Another symptom of a bad or failing headlight bulb is flickering headlights. If the headlight bulb filaments become damaged or excessively worn it can cause the bulb to flicker. A flickering bulb will usually burn out soon after the issue has begun. A flickering bulb can also be a sign of a bad harness or connection, so a proper inspection is highly recommended.

3. Headlight is out

Another, more serious, symptom of a bad headlight bulb is a headlight that is out. With regular use, headlight bulbs will eventually burn out and cease to function. A headlight that is out is usually a sign that the headlight bulb has burned out and needs to be replaced. It is recommended to replace them in pairs if possible, as the opposite headlight will also usually be near the end of it’s service life if one of them has burned out.

The headlights bulbs are some of the most important bulbs found on any vehicle as their light provides visibility and safety, which is required in low light driving situations. If your vehicle is displaying the symptoms above, or one of your headlights has burned out, have the vehicle diagnosed by a professional technician, such as one from YourMechanic, to determine if the bulb should be replaced.


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