I have a 2005 Jayco hybrid. Last fall, after a heavy rain storm, I noticed there was some black/brown coloured stain on one corner of the A/C (inside the trailer). I popped open the inside cover but c...
ditto on tightening the 4 main bolts first, that's the only seal between the roof and A/C. You probably has a fresh air vent though that could allow water in if the cover is cracked. Dirt builds up under the cover so the brown water might be from that. Some simple PL premium construck adhesive on the cover could fix any visible cracks.