Moisture trapped in tail light

I've had several cars over the years with this problem. Dealer usually tightens this and that with no effect. I usually end up drilling a small hole at the bottom and that takes care of it.

 

I have taken out/replaced the tail light assemblies on my Gen II.
My thoughts:

The moisture could only have gotten into an uncracked tail light one
of two ways:
* Through an incompletely sealed joint between the clear lens and
the reflector/housing, or
* Getting past the perimeter gasketing around the hole where the
light assembly mounts to the body, and then through the mounts
for the light bulbs themselves, (This gasket also keeps water out of
the car -- if its bad, water can collect in the spare tire well.)

In either case, if there is water (vapor) in the light assembly on a
new car -- never in an accident -- something is not right. Either the
lens to reflector seal is compromised, or the gasket is faulty.

It is probably a faulty gasket. They are quite soft and easily folded
over when the light is put in place. I would call that a manufacturing
defect. I do not expect a dealer would agree!

You may be able to do some investigating on your own.

If the 2010 tail lights are like the Gen IIs, they are held on by two
threaded studs afixed to the reflector and two plastic nuts.
Here's a thread on replacing Gen II lights:

http://priuschat.com/forums/gen-ii-...423-2007-tail-light-removal-instructions.html

I would stress that when you are putting the lights back in, DO
NOT cross-thread or overtighten the nuts on the studs. If you
goober up the threads or break the stud, a new Gen II tail light
assembly goes for ~$110 used -- who knows what a new high-zoot
Gen III light assembly will cost!

As to how to get the water (vapor) out, I think you'd have to gain
access to the back of the lights, remove the light bulbs, and blow
cool air, or only body temp air, through the light to evaporate the
water. I have no idea how long it would take. I would not go drilling
any more holes in anything to try to fix the problem.

 

The advice above looks best.

Dont drill holes.

I had a tail light lens on my pickup crack and it let moisture in. So I drilled a hole in the bottom which made dust circulate into the crack and dust up the lens.

 

I was just pointing out what has worked for me several times over the years and after dealers tried several times to fix the problem. Two inches of water sloshing around inside my light assemble was unacceptable to me. So was replacing the whole assembly which was what every one of them wanted to do after two or three unsuccessful attempts to stop the leak.
1/32 hole only, at an angle, in the most inconspicuous place along the lowest point of the liquid s what worked for me. Certainly don't take a 1/4 inch bit and start drilling holes in your car!

 

Rokeby covered it nicely.

I agree, do not drill a hole in it to fix the problem. If it was out of warranty then you might consider it as an option if you didn't want to seal the lens or gasket but not on a brand new car.

 

I agree. I think I used a 1/16 hole.

 

This is caused by poorly sealed light assembly or a crack has developed somehow.
If it is still within warranty, demand to have it replaced. It is not easy to fix since air can get in easily if not sealed correctly.
If you don't get it fixed, it gets worse, of course.

 

On an old car, I also have drilled a tiny hole. Combined with some additional sealing of the body crease that let water seep past the gasket (must have been factory damage, as its local siblings had the same problem on the same side), it worked. It didn't add enough air circulation to cause any noticeable dust accumulation over its next decade.

A GenIII is still under warranty, so make the dealer fix it.

 

I saw the same thing but it dried up eventually- if it get's really bad, I will ask them to replace it.

 

I had to have body work recently that required removal of the panel adjacent to the lens. I was notified by the body shop (before they did the work, fully covered by insurance), that the seal (I think between the lens and the bulb, but not sure) was not there. That is, it was not installed at the factory (2010 Prius III). They told me I should take it to Toyota because this might eventually cause the problem you describe. Sounds like someone fell asleep at the factory. I'm taking this to the dealer to correct.

 

My car's rear top left taillight has moisture as well at the very top of the plastic. The other one is fine. I haven't checked today, but I guess I'll have to look into this issue as well.

 

Hi guys,

I also recently noticed condensation on my rear right taillight after some heavy rain. Brought it to dealer to complain, and they agreed to replace it with new one. Should be done today. I will post if anything new.

 

Replaced with new taillight under warranty, good to go for now.

 

How to fix water trapped in your tail light