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Old 06-06-2019, 07:42 PM   #1
Join Date: Jul 2018
Posts: 53
Moisture stain under AC vent

Found this stain around the vent that is directly under my Class C AC unit (in the center of the coach ceiling) The stain cannot be more than 5 days old. The stain is dry and there is no moisture on the roof (ac unit) or inside the vent.

What are potential causes? The stain seems too large for simple condensation.

I ran the unit for 20 mins, shut it down, and returned 2 hours later - the ceiling was dry.

I appreciate any trouble shooting tips. I plan to take it out this weekend and get it looked at after the weekend, unless it is a project a novice can tackle.

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Old 06-06-2019, 07:58 PM   #2
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Join Date: Apr 2011
Location: Powell River, B.C.
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It would appear that the condensation that should run out across the roof from A/C operation is not going out the drain onto the roof and got deep enough to run inside the coach .

You'll have to get onto the roof and remove the covers , to get to the condenser drain pan , ( white tray under the condenser) and check the corner drains .

Phillips screwdriver, for top cover , 1/4 and 5/16 nut drivers, for the tin cover on the condenser , needle nose pliers, Q tips and rags.

A/C unit clean out should be done at least every second year , annually if used in dusty conditions.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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Old 06-07-2019, 06:41 AM   #3
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A/C gasket? When my A/C drain was clogged it dripped inside the RV.
Todd & Nadeen :: FMCA F484487
2014 Tiffin Allegro RED 38QBA pushed by Tiny (2020 Nissan Versa)
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Old 06-07-2019, 07:48 AM   #4
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I did some research and it seems like the A/C gasket. I will inspect both the drain holes and gaskets later today. I found some instructional guides on fixing the gaskets, but I am open to feedback on how to fix this. I plan to take it out this weekend and run the AC. If I find moisture when running the AC, it seems more likely that there is a problem with the unit. If I find moisture after the rain (expected Sunday), it is likely the gasket.
2012 Winnebago Vista 35F
Stoddard, WI
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moisture, vent

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