Haynes Tech Tips - Headlights
Can you see water droplets inside your headlights?
Modern cars use separate headlight bulbs inside clear plastic housings. The water seals on the housings can sometimes fail and allow the housing to fill with water. This can lead to early bulb failure and diminished headlight performance when the housing “steams up.”
The housings are usually easy to remove (see your Haynes manual). Then you can shake the water out and look for the bad water seal or crack that caused the leak. Cracks can usually be sealed with clear silicone sealer. A hair dryer will speed drying the inside of the housing.