Help! Bubbles on the ceiling!

[SJR/MB from Maine]

First night in our new to us Montana 3160RL. Sitting in the recliners and I look up, and wow! Our rig sat in the side yard here in Maine for the winter. We kept the vent covers open, as recommended, for condensation. No water leaks are visible anywhere, just the bubbles. They are hard to the touch, not soft at all. It is in the rear of the living room, just over the pull out couch. Help!

[TexCamper]

Looks like it might be a water leak. Some people get this if there's a window nearby that may not be sealing properly. You may want to get on the roof and look for a gap in the sealant or a tear in the roof covering near that wall.

[SJR/MB from Maine]

TexCamper, it’s only on the ceiling, not on any walls. It is under where the ac unit is. Could it be from that? No roof tears or gaps anywhere.

[TexCamper]

Originally Posted by SJR/MB from Maine

TexCamper, it’s only on the ceiling, not on any walls. It is under where the ac unit is. Could it be from that? No roof tears or gaps anywhere.

It’s really hard to see where it is from your pictures. But if it’s on the ceiling and near the AC unit, I would suspect a leak at the AC unit. These little hard bumps tend to be how the wall can look when there is a small water leak. One other thing it could be is condensation in the attic space on the air duct that’s making it’s way down to the ceiling. If your unit is under warranty I’d take it in the dealer and have them look at it. Stuff like this is nothing to let go. It can go from bad to worse if it continues.

[psomers]

I have something very similar. I have two AC and the panels the AC are mounted have a black stain. All the other panels are ok. I have taken a ceiling light out and ran a borescope into the attic. My panels have the bubbles on top of the panel. I'm sure it's caused by condensation. I have resealed the AC duck work but black stain continue to get worse. The big box stores sell a spray stain blocker. It is made for ceiling and sprays almost straight up. Didn't completely cover but is much better.

[SJR/MB from Maine]

We had to replace the attic vent cap last year, could it have something to do with that?

[psomers]

Originally Posted by SJR/MB from Maine

We had to replace the attic vent cap last year, could it have something to do with that?

Have thought about installing a vent cap. The Mountaineer doesn't have a vent cap. With out a real cavity in the attic wasn't sure about their usefulness.

[TexCamper]

Originally Posted by SJR/MB from Maine

We had to replace the attic vent cap last year, could it have something to do with that?

It’s possible that the vent cap might have blocked the attic vent instead of just keeping the rain out. It’s also possible that walking on the roof caused a crack in the sealant somewhere.

Are the bumps underneath or a little behind the rear AC unit? I’d check for a poor sealant job around the rear AC. It might require removing the AC cover to really inspect the seal. When you think about causes of moister on the rear part of the ceiling, the rear AC unit can be a good place to look first.

If there’s an attic vent back there also check it for good sealant around it. Putting the vent cover on it might have cause a gap between the sealant and pipe when the vent cap was pressed on.