Yep it was the third break light. Bbout a half inch gap between the light and the cab with no seal in between. The assembly is filled with water. Not something I really want to fill with silicone either as it looks like some would get inside the housing.
So the question is now do I need the headliner replaced? Im worried about mold in the future. Or can I dry it out with the windows down, maybe a blow dryer?