My 2004 4.4 had (has) the same issue. Light assembly was rusted out and the dealer replaced the whole light assembly and painted to match the vehicle color. It worked for about 4 months and is now doing it again. I removed the clear plate light lens and water dripped right out of the assembly so I imagine that I will be getting it replaced again. My question is - where the hell is the water getting in and how is it getting in so far that it is f#$king up the wiring harness?