I had a fair amount of moisture in my drivers side headlight about 1 year back, ..it occured in the autumn time after a particularly long wet spell. The moisture stayed there for a good 6-8 weeks, and it was affecting the beam since it was on the inside of the acrylic lens..but eventually dried out with use of the lights. Stealers confirmed this is common and to be expected, and that is was not preventable since they are designed to allow airflow in and out of the units. The fix as already stated is get your hairdrier on it, or since mine was never that bad, just go out and drive and it will go.
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