Originally Posted by Inland RV Center, In
Check the "sewer vent pipe cover gaskets."
They are good for 5 to 6 years,. at best.
and this is exactly what happened on my trailer. bad sewer vent gasket...water dripping over the end of the bed, probably 8-10 feet away, and the ceiling seam is up higher than the vent! what happens is that the insulation in the ceiling soaks up the water, and it can wick it uphill. it could come out "anywhere".
I suspected the AC, too, as its the closest thing. But that wasnt' it. Not that this isn't your problem...it could be. different models of AC attach to the trailer differently, so exactly how/what to look for will vary. But as Andy says, that sewer vent is a very likely culprit.
I only got a drip inside when it was really raining hard. big "downpours". In light rain, it wasn't noticeable. I'd have to draw a diagram to explain it, but it makes sense.