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 HID bulb reaching the end of its life.
Was the headlight bulb recently changed? It may have been changed with a bulb that had different color temperature making it appear different or dimmer than the other headlight.
|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 volt.