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Roof AC leak.

July 13, 2019, 12:01:05 am

I was up on the roof today, putting some things away and I must have cracked some caulking around my rear AC.
 I developed a drip around the inside cover where there was never one before (old style Coleman) and the ceiling is wet by the unit.
 I have a tube of lap seal (the RV kind) stashed away but its 18 months old (never opened).  If my emergency stash is bad, would regular silicone caulk work?
TIA.

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Re: Roof AC leak.

Reply #1 – July 13, 2019, 06:58:55 am

Moby, it will work for a while, get area really dry before applying. If neither component is plastic and if you want to preserve your ability to disassemble the joint, use polysulfide. If you want a permeant  joint use polyurethane .
Chris

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Re: Roof AC leak.

Reply #2 – July 13, 2019, 07:55:54 am

There is a gasket under that unit. Remove the ceiling cover, remove the 3 (I think) bolts and disconnect the plug, then the roof cover. Tilt the whole unit on it's side. Scrape off the old gasket and apply a new one or strips of butyl rubber from Home depot cut to size and put the unit back down. Reconnect everything and you've done it right.

Naturally, I always assume everything is like mine.

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Re: Roof AC leak.

Reply #3 – July 13, 2019, 08:45:18 am

You do NOT want to use calk unless it's a real emergency, must rv dealers carry a generic AC roof gasket from Camco which should work- about $20
Do not over tighten the bolts when reassembling, only need to compress the new gasket by about 30 percent
A plastic 1.5" scraper is helpful getting the old gasket off the underside of the AC without scratching the paint
Good luck

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Re: Roof AC leak.

Reply #4 – July 13, 2019, 09:02:34 am

Correct-- NO sealant.

You can try to compress the gasket a little more (4 bolts inside ceiling unit), but really by far the best solution is to replace the foam gasket-- torque bolts to compress gasket 1/2 of initial height.

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Re: Roof AC leak.

Reply #5 – July 13, 2019, 10:26:30 am

I had both gaskets replaced on my AC units, they just age out and you get to where you can't tighten them any further, and as already indicated, don't tighten them too much when you replace. A word of caution, this is ideally a two person job as it's much easier to lift and reinstall AC with four hands. A local man fell to his death replacing his unit. It was stuck, he used a lot of force to break it loose and went over the side and landed on his head when it came unstuck. The gaskets can be picked up at almost any RV repair shop or received within a day or two via Amazon. There will be mold around the opening so have some bleach water in a spray bottle handy and give it a little dry time. Good time to also clean coils and replace or clean foam air filter.

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Re: Roof AC leak.

Reply #6 – July 13, 2019, 10:36:35 am

Yup, two people on roof.  And a 1/2 sheet of plywood or thick cardboard to set the A/C upper unit on while you clean the opening-- you don't want to scratch the roof.

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Re: Roof AC leak.

Reply #7 – July 13, 2019, 11:08:56 am

One other idea to consider - when replacing the gaskets, do you stick them to the underside of the A/C unit, or to the roof?

I recommend sticking them to the underside of the A/C unit.  Here's why:

When we recently had both our A/C units replaced, the installers found one old gasket stuck on each way.  One was stuck to the bottom of the A/C, and one was stuck to the roof.  The one stuck to the roof caused a LOT of extra work getting all the very sticky adhesive residue removed.  So do the next coach owner (or yourself) a favor, and stick the new gasket to the underside of the A/C unit.  Then, if the A/C units ever need to be replaced, it will be a much easier job for the installer.

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Re: Roof AC leak.

Reply #8 – July 13, 2019, 12:28:38 pm

Don't assume it is the gasket causing it to leak.  Check to make sure there are no cracks in the plastic shroud.  If there is a crack in the shroud it will leak into the AC and it might look like it is coming from the gasket.  If you find a crack in the shroud you can use eterna bond tape or Duct tape to temporarily fix it until you can get a new shroud.  Also make sure your drain holes in the bottom pan are not plugged.

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Re: Roof AC leak.

Reply #9 – July 13, 2019, 02:26:12 pm

Crud.
Wish I waited longer before attacking the problem early this AM.
No replacement gasket available.
I took the next available route.  Found no tears in the gasket but located where the water was coming in.
Cleaned roof well, applied non leveling sealant to mating surface and joined together.
 Will see how stupid I was.
P.S.
 Looks like PO had a similar problem.
They attempted to fix by caulking from the inside.  Hey, it worked for a while

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