I searched thoroughly here, and I have seen a lot of threads describing headlight fogging and condensation, but none of these threads indicate if there was damage to the headlight assembly, the bulbs, or wiring.

There is a Technical Service Bulletin from Nissan describing headlight fogging (condensation) and the remedies. The TSB describes the problem and differentiates fogging from “water collection” inside the housing. The TSB states that “water collection” is a problem (and a rare occurrence) requiring replacement of the housing. The typical problem is “headlight fogging” which the TSB says is self-correcting does not require intervention.

I recently experienced “headlight fogging/condensation” (and this is after owning the car 16 years and never seeing this before). I’m in an area that has had a very atypical winter (lots of snow, then rain and ice, and also very frigid temperatures on and off).

My question: Has anyone experiencing headlight fogging/condensation sustained damage to the headlight housing or wiring that required a significant repair?

 

Actually a great question. I'm lucky, 2006 ZR, original bulbs @ 106K, only experienced a little UV damage if left in the sun. 0 water or condensation problems. Have the housings ever been opened?

 

The housing as never been opened. I don't think this is pertinent because the housing has a vent (to prevent the problem I describe).

 

Your question about opening the housing is actually very good. I started thinking about this, and I forgot that early in the winter my front passenger fender liner came loose. I refastened the liner, but it is the passenger side light that is fogging. I wonder if the loose fender liner was the cause? I'm guessing, but maybe some moisture from the tires was thrown into the light's vent.

 

Even something as simple as swapping a bulb can let enough humidity inside the housing to cause some condensation, depending on humidity conditions. You'll notice it more if there is a larger humidity difference (my worst humidity experience happened when I sealed headlights indoors on a super humid day)
The vent is supposed to allow the headlight to correct on its own, but it can take months in some cases. You can always check to make sure it is not blocked.
Generally speaking, fogging will not cause electrical issues, but will make your lights dimmer.

On the 06+ I usually remove the lower parking light bulb, run my shop vac up to the opening with a nozzle attachment, then hit the outside of the lens with a hair dryer or light heat gun whenever it's condensed. That provided the most immediated successful results.
I've also tried the desiccant packets for food (like in beef jerky) which have some success but take a long time compared to just running a vacuum to pull some air.
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Agreed. I try to ask the obvious q 1st. So then, are you able to remove the drain tube and ram a pipe-cleaner/small guage wire in to confirm it's draining correctly?

 

If the OEM vent tubes are clogged/dirty or can't be cleaned which is preventing the housings from properly venting moisture, TRS sells a bolt-on breather kit (which would involve separating the housings) or 3M Goretex patches to let moisture out.

 

Thanks for the tip. I'll check the drain tube.

 

If you've hit the front of your bumper or scrapped it on anything before, it distorts with other parts including the fender which then puts stress and strain on various parts especially the headlights. I've had a few issues from scrapping, parking blocks etc that has caused some condensation to form in the headlights after a wash. You can use butyl rubber glue which is the same sealant used from the factory. Take your headlights out and reseal the edges where the lens meets the housing, check other areas for possible water entry.

 

Many thanks to moderator jhc for the solution to my condensation problem. His suggestion to clear the vent solves the problem.

I think that the condensation problem started when I loosened my passenger side fender liner. mr. sparco mentions the cause of this problem: "If you've hit the front of your bumper or scrapped it on anything before, it distorts with other parts including the fender which then puts stress and strain on various parts especially the headlights. I've had a few issues from scrapping, parking blocks etc that has caused some condensation to form in the headlights after a wash."

And... Accessing the vent is not easy.