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Old 08-18-2022, 09:01 PM   #1
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Trying to seal roof top A/C units

Does anyone have any experience sealing around the roof top A/C units. I have had the top half of the covers off of the units but there doesn't seem to be any way of removing the lower half of the covers without some dis-assembly of the a/c units themselves. I have had a serious water issue with the front unit on a previous motorhome and don't want to go through that again. Without getting the lower cover off, the sealant is not even visible. Can you get at the sealant from the inside? Anybody?
Jim & Millie
2015 Georgetown XL 377TS Ford F53
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Old 08-19-2022, 06:32 AM   #2
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What make and model of air conditioners do you have? None use "sealant" that I know of and all use a foam gasket instead. If you have Atwood roof units as we do:

Remove the inside panel with the filter and the other one with the dump vents. You'll see four bolts, one in each corner. Ours on our Atwood AC-1511 units are 11/16" but others have reported different bolt head sizes.

Those four bolts should be checked for tightness once a year as they will loosen up. There is a foam gasket on the roof between the roof and the roof unit. That foam gasket needs to be partially compressed.

If those bolts are loose then water will get inside the motorhome. Some people have posted videos of it literally raining inside from the air conditioner when those bolts are loose. If the bolts are cranked down tight then the foam gasket will be squashed and water will get inside the motorhome.

But Atwood did not leave enough room in the thin plastic frame screwed to the ceiling on ours to be able to place a socket directly on the bolt heads.

If you have that bolt head access problem, remove the screws holding the plastic frame to the ceiling and use a file to enlarge the holes so you can place a socket on each bolt head without needing to remove the frame in the future. Then screw the panel back to the ceiling.

Those four bolts should be torqued to 4.4 ft lbs (four point four, not forty four). That's not super tight, just snugged up.

4.4 ft lbs is not much torque. I just put a socket on each bolt and tighten them until they feel snug. DO NOT fully tighten them.

Hope this helps.

2020 Georgetown GT5 34H5
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Old 08-19-2022, 09:25 PM   #3
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Thanks for your reply Ray. My ac units are Dometic but i would think that they will be mounted similar to the Atwoods. I will take the interior trim off and have a look, now that I know what I'm looking for. I too had the misfortune of having a mini Niagara Falls coming through the front ac unit on our previous Georgetown. Don't want to experience that again. Your detailed reply will help me, and many others, and is very much appreciated. Thanks again Ray.
Jim & Millie
2015 Georgetown XL 377TS Ford F53
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roo, roof, seal

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