AC roof leak caused by tight fan shroud cover

[Bay955]

Hello once again I have water coming thru the ceiling in my 2019 Montana. I finally have this figured out but would like some input. When I go on the roof take the cover off the ac, then take the foam cover off that covers the radiator and fan all the water then runs out my drain holes as there supposed to. When I put the foam cover back on the water won’t release thru the drain holes. It creates a vacum then sucks the water into the fan, and there for puts it in my duct work. Soon as I crack the seal on foam cover again all the built up water releases. Should a put a few spacers in it to keep it from vacuum sealing. It will run all day with out cover and never leave thru the roof.

[Ram Montana High Country]

I had construction wood fibers that blocked drain hole under foam.

[Bay955]

Yes sir cleans those out and drilled a few extra. As soon as I put the foam back on it holds the water.

[twindman]

I have never removed the cover on my current rig AC. So is there some sort of filter on top of the trailer under the AC cover? Thanks.

[Bay955]

No just the suction side of the fan, and your other radiator.

[Butch & Kathy]

Several of us have had the Dometic Blizzard AC return leak issue. After a heavy rain water leaks through the return vents. See the TSB below.
https://static.nhtsa.gov/odi/tsbs/20...79726-2280.pdf

[Bay955]

Thanks. I have made all those corrections with tec. There is no leak in heavy down pour with ac off. My prob is there is a vacuum that is holding the water from exiting the drain holes. Clearly when I slightly lift up on the shroud cover and break the vacuum the water pours out the drain holes correctly.

[jimcol]

Have you tried to call the manufacture tech support. They hear product specific problems all day. Might have a solution.

[Bay955]

Good idea. Thanks

[Tom N OH]

Originally Posted by Bay955

Hello once again I have water coming thru the ceiling in my 2019 Montana. I finally have this figured out but would like some input. When I go on the roof take the cover off the ac, then take the foam cover off that covers the radiator and fan all the water then runs out my drain holes as there supposed to. When I put the foam cover back on the water won’t release thru the drain holes. It creates a vacum then sucks the water into the fan, and there for puts it in my duct work. Soon as I crack the seal on foam cover again all the built up water releases. Should a put a few spacers in it to keep it from vacuum sealing. It will run all day with out cover and never leave thru the roof.

What is the build date on your trailer? Mid year 2019, they added supports inside the return air ducts in the ceiling to hold them open better. Early 2019 & before did not have them & the ducts were collapsing under the suction of the A/C unit. Yours may be sucking the return ducts closed, creating a vacuum that is preventing the condensation from draining out of the rooftop unit.

[Bay955]

That for sure sounds like my problem.

[Bay955]

Good thing is, it’s a very short duct so iam gonna try to take the foam cover off today stick my ar back under see if I can feel it collapsed maybe put something in there to prop it up. I’ll let you know. Min was diff early 2019 model.

[Tom N OH]

There is a thread on here where people were cutting pieces of 1 1/4 or 1 1/2 pvc pipe & inserting into the return air ducts to hold them open. If you take the filters off the return air ducts on your ceiling, you’ll be able to see quickly if yours has the supports or not. Our 2019 3811MS was built in Feb of 2019 & it has the supports from the factory. It still holds a little moisture. It will drip off the outside of the roof when running, but when it shuts off, we get a bigger “dump” of water. Not enough for it to blow out of the duct with the cold air.

[Tom N OH]

Another thing that helped ours. When I took the filters off to look for the supports, the openings in the ceilings were not cut to the same size as the openings in the base that the filter snaps onto. I removed the foil tape from around the hole in the ceiling, traced the inside of the base opening onto the ceiling, cut it out with a jigsaw & retaped it. The A/C flowed a little better, which helps it to #1, not freeze up & #2, more of the water drips off the roof while it’s running.