My 97 dodge truck did this same thing this spring. I must have dried it out 5 times by removing the whole thing and putting it in the sun. I finally took some clear silicone sealer and with the headlight off the truck carfully ran a small bead on the joint between the clear lens and the black housing. Let it dry and reassemble. It has been about 4 months and no moisture has reappeared yet. With any luck it's a pemanent fix.