Keystone Cougar - Installing 2nd AC - Roof cut

[xanth]

Have a 2016 Keystone Cougar that was wired for the 2nd AC.

Last weekend, removed the vent and put up a 2nd AC, an Dometic Penguin II.

Fairly easy to do, but getting the old sealant off was a pain. And in some places, it just didn't come off (it was stretching the roof membrane, tearing some of it, ect).

Anyways, cleaned it up the best we could, got what we could off, noticed a tear in the roof that was about 1/2 outboard of where the roof opening was, maybe 4-5 inches long..

Well, the seal for the AC covered up the cut in the roof, so I decided to roll with it, install the AC and see how it looked.

Looks fine (IE the cut is under the AC seal as far as I can tell). Doesn't seem like it is leaking, at least nothing obvious, but I know where it would be leaking wouldn't necessarily be noticeable from the hole.

Anyways, second guessing myself now, thinking I should just pop it back off and put some 4" Eternabond tape (just found out about this stuff) basically on the outside of the AC hole in the roof, then mounting the AC back up.

I have read lots on people using Eternabond on the seals and what not on RV roofs with great success, but haven't seen much about using it under an AC.

One of the concerns I have doing it, is when the tape is overlapped, it will create not perfectly flat surface, and quite possible a way for water to flow between the tape and the AC seal.

Any opinions?

Anyone used the tape under an AC? Any issues?

Thanks for the help!

[4x4van]

Yup, which is only 3-4 ft/lbs; very light.

[xanth]

4x4van wrote:
Don't overtighten the A/C unit. Just a turn or two past snug is all you want.

Good advice! The directions actually had a torque setting in there, 40-50 inch lbs, so followed that.

[4x4van]

If the roof material is bunching up, then it sounds to me like you are overtightening the A/C. Don't overtighten the A/C unit, just a turn or two past snug is all you want.

[xanth]

Thanks everyone.

Went with the 4" tape around the opening, then the AC unit on top. While I haven't driven anywhere, seems to hold up to the rain storms we've had.

Hopefully it works out, a little bothered by how much the roof material bunches up on the outside of the AC when you tighten it down, but don't want to take it off again, so we will see.

I did a ton of researching about installing one of these RV, but didn't see much (if anything) as to what's OK and what is not. IE is the roof material bunching up OK? It doesn't seem so (it is on the front side), but not matter what I tried, it bunched up as I tightened down the AC.

[A1RVTraveler]

My vote is the 4-inch Eternabond all the way around the opening. It covers any small cuts you may have put in the roof removing the old sealer and gives a nice surface for the AC gasket.

[allen8106]

Dicor would be my choice in that spot. the tape will create an uneven surface with a potential for a leak.

[CincyGus]

I think I would have done dicor over the cut prior to mounting the AC, then cleaned and sealed the edges of the AC cover with eternabond after a week or so.

Dicor is a great sealant, it just doesn't have the staying power that Eternabond does, needing touch up after somen weathering. Eternabond is super sticky, doesn't come up easily and is a nearly permanent fix when applied on a properly cleaned and prepped surface.

[agesilaus]

Eternabond is one possibility. But I would have given the cut a coating of Dicor no matter what else you do. Under the flap and on top. Eternabond also has some thickness, I'd guess at least 1/8 in thick, maybe a little more. You might think about that Gorilla sealant tape over the Dicor. It is thin.