It is not uncommon for one of the headlights on your car to be dimmer than the other side. In this guide, we take a look at common problems that cause one headlight to be dimmer than the other side. 

Symptoms

  • One headlight dim and the other bright
  • One headlight is dimmer than the other side

Common Problems

headlight too dim

Bulb Age

A dim headlight on one side is in most cases caused by a light bulb that has reached the end of its life. 

Wrong Light Bulb Wattage

On cars with HID Xenon headlights, it is common for one of the headlights to be dimmer than the other. This is often caused by an HID bulb reaching the end of its life. 

Bulb Not Installed Properly

highlight dimmer

It is possible that one bulb is dimmer than the other due to a bulb not having been installed. If the bulb does not sit correctly in the headlight socket shown above, the headlight will not project the light correctly, making it look dimmer than the other side. 

Headlight Misaligned

headlight misaligned too dim

This is a common problem after an accident. The headlight assembly may be misaligned causing the beam to point to low and thus making one headlight look dimmer than the other side. 

All headlights can be adjusted. 

Foggy Lens

foggy headlight

A foggy lens may also be the reason why one headlight looks dimmer than the other. This can be an issue if you replaced one headlight assembly but not the other. Use a headlight restoration kit to restore the foggy headlight to like-new condition. 

What should I do if one headlight is dimmer than the other? 

First, find out if the headlight bulb was recently changed? It may have been changed with a bulb that had different color temperatures making it appear different or dimmer than the other headlight. 

Possible Causes

Headlight Brighter / Dimmer Headlight Different Color
Bulb reaching the end of life Different Bulbs
Weak Ballast Bulb reaching the end of life
Poor connection or ground  

To fix the problem where one of the headlights is dinner or brighter than the other you will need to remove the dim bulb and replace it.

If that doesn't fix the problem, check the voltage to the bulb. A short or poor ground can cause the voltage to be less than 12 volts.