OK, I'll share, as I always do, the method I used, very successfully to not only remove water condensate, but to remove the grungy haze from the inside of the headlight housing.

Please bite your tongues until you try it. Alaxfire will attest to the efficacy of this.

You will need one liter of at least Laboratory grade Methanol. 99.8% or better. I used Electronics grade 99.8%. When this evaporates, it leaves nothing behind. This is very important.

DO NOT use any other solvents. I know methanol works and is safe for this use. If you pour acetone or Trichloroethane or paint thinner because "that's all I had" in there-it's your fault and your problem.

I recently polished a couple of pretty shot headlights and couldn't get the sparkling clarity I was expecting. I went through the 500P/800P/1500P/Trizact 3000P cascade 3 times and was getting pretty cross. Curious, I put a long Q-Tip in a hemostat and swabbed a spot on the inside of the lens. It smeared the gook in there. I've read about the intrepids that used a pair of magnets and a scrap of MF towel to clean in there with some success.

I poured in ~ 1/4 pint of the super-dry methanol through the eyebrow lamp hole and swished it around for 2 minutes. Poured it out and then dried it with a heat gun, lens UP.
I repeated this 3 times. The results were surprising: What I would have sworn was poor polishing on the outside turned out to be an even coat of contaminated condensate on the inside. Each iteration of this "rinse and repeat" step increases the ratio of gook to solvent.

Now, as to where this is headed. When I mentioned "...contaminated condensate..." earlier, I meant exactly that. The headlamp housings "breathe" as they heat up and cool down. When they "inhale" (as they cool) they suck in air, water vapor and whatever crap is in the air at that time. Smog, oil mist from the engine bay, beer farts, whatever. All of this crap condenses on the interior surfaces in an even coat and will remain there, building up, forever.

This procedure cleans them very well.

A lesser purity grade will cause water spotting on the inside. Yes, that .2% is water. And it will spot. DO NOT USE Isopropyl alcohol of any grade/purity. The semiconductor industry uses methanol for a very good reason-no residue after evaporation.

Using this method and the cap kit ( P/N 5174786AA) cited in this thread:

https://www.crossfireforum.org/forum...tml#post659136

should result in a long-term solution to this problem. It worked for me and G.

Don't worry about crazing in the short time the methanol will be in contact with the polycarbonate (Lexan) lenses. It is a recommended solvent for short (< 180 HOURS) periods of time:

http://www.theplasticshop.co.uk/plas...sing_guide.pdf

Info on different grades of Methanol:

Methanol - Solvent by Type | Sigma-Aldrich

(Page 25) (Also please note that this is a General Electric bulletin for Lexan. They should know.)

I hope this helps.

YMMV

Methanol Vapors are explosive/combustible.