Headlight has moisture in it

What causes moisture buildup in front headlight of my 2006 Toyota Sienna van? How can I correct it?

Your headlight is a sealed “lighting module” the seal of which has been breeched. These modules are not designed to be disassembled. If you can remove the module and find the breech you might be able to seal it with an RTV silastic (like 100% clear silicone from the hardware store). Short of that, the only solution is to replace the module. Not cheap.

My lights in my Ford Explorer have a ‘weep’ hole in the bottom. I know this, because I did some ‘home repairs’ on a fender-bender my wife had. If these ‘weep’ holes become clogged, which is easy because they are small, moisture from the air can easily accumulate, and have very little means to escape. They’ll just keep building up. Look under the light unit where the lens is attached to the casing.

I didn’t think the newer cars had sealed beams, my new toyota doesn’t…if you check the manual and you can change the light bulb then you might try removing the bulb and dry out the area with a hairdryer…

It’s not a ‘sealed beam’ in the true sense of the word but rather an assembly where the glass is ‘sealed’ to the rest of the assembly. The bulb holders turn 1/4 left to unlock and remove to replace a new bulb. Reverse for installation.

Caution: do not touch the glass of the bulb with bare fingers as this will shorten the bulb life.

Headlamps today are a bad joke IMHO. My headlamps (glass/plastic?) fogged up too. I drilled a small hole to drain the water out, dried the unit out, replaced it back on the van and the next day it was fogged over again.

At 200 beans to replace one, it’ll be a long time before it gets done.

I drilled small holes in the bottom or the lights that did this for me on my vehicles. There is no easy fix and a new unit may do the same, eventually. The moisture will corrode the fixture for the light and that will cause you to lose the light. If you get fogging the light should generate enough heat to remove the fog–just leave it on long enough.

I just had a thought…
It might be the seal around the lightbulb socket where it’s screwed into and seals against the rest of the module that’s leaking. Are the sockets fitting snugly? Are the sealing O-rings at the bases missing?