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  1. #1
    Super Member
    Join Date
    Apr 2000
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    8,159
    Location
    Shingle Springs California
    Tractor
    New Holland TC40D

    Default 5th wheel AC leak

    I keep getting a leak at the AC unit on my 5th wheel.

    We got it used three years ago. Unfortunately, near the end of our 4500 mile round trip to Texas right after we got it, the rubber roof liner went on us(peeled back 10' while we were on I-5). So, I learned how to replace a rubber roof with help from a couple friends that had worked in RV repair. Everything about the roof replacement has worked great, except the AC unit.

    The first year after the roof replacement, I got a leak. Tightened it down, and that helped for a while. Wound up having to replace the foam seal. That worked thru last year. Now, I have a leak again. Nothing changed on the AC unit. When I replaced the seal last year, the roof looked and felt nice and flat where the AC mounts.

    The seal is compressed about 1/2 way, like the directions say(I have all the original paperwork for the AC, including installation). If I tighten it more, it will tighten the AC weep holes will be against the rubber roof.

    My wife thinks we should just caulk around the seal.. The directions don't say to do that, and neither did my RV repair buddies(have lost contact with them; they both moved).

    I'm not sure what to do...

    Anyone had a solution to a problem like this? I'll try to get some pictures in the AM.
    RobertN in Shingle Springs Calif

  2. #2
    Silver Member
    Join Date
    Mar 2010
    Posts
    127

    Default Re: 5th wheel AC leak

    Are you sure that it is coming in around the seal? Most modern RV roof frames are many sections of box tubing welded together, it's easy for a leak to travel inside a tubing and come out somewhere else.

    With almost 20 years RV repair experience, I can say that on older RV's with uneven roof surfaces or sagging braces around the AC it can be necessary to apply silicone around the gasket before lowering onto the roof. However, this is not necessary on a roof in good shape.

    Could it possibly be condensation?

    If you have a decent RV repair facility near you, inquire if they have a SealTech machine. This is a machine that attaches to a roof opening and creates a positive pressure in the RV, forcing air out potential leak points. The tech goes over the RV with a soapy water solution and bubbles show at trouble spots.

    Can you give more information as to the conditions when the leak occurs?

  3. #3
    Super Member
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    Apr 2000
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    8,159
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    Shingle Springs California
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    New Holland TC40D

    Default Re: 5th wheel AC leak

    It did not leak for a while after I snugged the AC down tighter. I was wrong above; I followed the directions both times reinstalling the AC with new gasket; the book says it should compress the gasket 1/4".

    That 1/4" just did not seem to be enough. After a year with a few trips to the coast, it settled, both times it would seem.

    The 5th wheel is a '98. The roof is good; the wood etc is solid.

    It leaks when it rains. We only used it really on our first trip, before the rubber roof peeled back on the highway. Most of our trips are to the N. Calif coast, where dont need AC...
    RobertN in Shingle Springs Calif

  4. #4
    Super Star Member Diamondpilot's Avatar
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    Jan 2007
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    15,308
    Location
    Daleville, IN
    Tractor
    Jinma 254/284 Ford 861 Powermaster at work

    Default

    I would remove and install again with a new gasket or better yet two. We use the same units on house boats and always apply a big bead of silicon, I am talking 5/8" or so, before setting it in place.

    Chris

  5. #5
    Super Member
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    Apr 2000
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    New Holland TC40D

    Default Re: 5th wheel AC leak

    This is one of the only pictures I have... From when we first got it. I'll try to get more today of the AC unit, but it is raining...
    Attached Thumbnails Attached Thumbnails -dscn0321-jpg  
    Last edited by RobertN; 11-17-2012 at 09:06 PM.
    RobertN in Shingle Springs Calif

  6. #6
    Super Member kenmac's Avatar
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    Feb 2005
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    6,273
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    The Heart of Dixie
    Tractor
    yanmar 3110D

    Default Re: 5th wheel AC leak

    if you have a rubber roof. Don't use silicone. I use eternabond products and have had great results
    A Fredricks Yanmar 3110D
    07 Dodge 2500 5.9 Cummins
    Husky 372xp
    Husky 55 Rancher
    Maruyama trimmer
    Husky trimmer
    Redmax BP blower
    Toro zero turn
    North Star 4 K PSI pressure washer
    Honda 300 4 trax
    Yamaha Timberwolf
    liquid logic coupe kayak
    16' Tow Master Dump Trailer ,20' Yanmar Hauler

  7. #7
    Super Member
    Join Date
    Apr 2000
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    8,159
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    Shingle Springs California
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    New Holland TC40D

    Default Re: 5th wheel AC leak

    I was wondering about that. I still have a tube of the caulking used around vents and screws(the kind that "flows"). I don't think that stuff would work.

    There are a couple RV places local; they must have "caulk" like that. Rubber roofs are on everything... I want to start with new seals anyway.

    Quote Originally Posted by kenmac View Post
    if you have a rubber roof. Don't use silicone. I use eternabond products and have had great results
    RobertN in Shingle Springs Calif

  8. #8
    Super Member kenmac's Avatar
    Join Date
    Feb 2005
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    6,273
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    The Heart of Dixie
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    yanmar 3110D

    Default Re: 5th wheel AC leak

    I order mine on line. Just ordered 4 more tubes to have around ( $33.00 with shipping). They (eternabond) also has a tape that I have used to seal around the front & rear cap & vents. I believe I used the tape around my A/C unit as well
    A Fredricks Yanmar 3110D
    07 Dodge 2500 5.9 Cummins
    Husky 372xp
    Husky 55 Rancher
    Maruyama trimmer
    Husky trimmer
    Redmax BP blower
    Toro zero turn
    North Star 4 K PSI pressure washer
    Honda 300 4 trax
    Yamaha Timberwolf
    liquid logic coupe kayak
    16' Tow Master Dump Trailer ,20' Yanmar Hauler

  9. #9
    Silver Member
    Join Date
    Mar 2010
    Posts
    127

    Default Re: 5th wheel AC leak

    There is nothing inherently wrong using silicone under the AC gasket. Silicone is not the correct sealant for the roof seams or attachments, for that you need a self-levelling elastomaric sealant that is compatible with your rubber roof. I don't use self-levelling sealant under attachments because it never really dries.

    Most RV's use Alpha sealants on rubber roof material, sometimes Schnee-Morehead.

  10. #10
    Super Member kenmac's Avatar
    Join Date
    Feb 2005
    Posts
    6,273
    Location
    The Heart of Dixie
    Tractor
    yanmar 3110D

    Default Re: 5th wheel AC leak

    I have used self leveling .I didn't like it. I like the eternabond brand caulk. I must have missunderstood. I thought silicone was going to be used on the outside area around the the A/C flange ??? where it meets the rubber roof.
    A Fredricks Yanmar 3110D
    07 Dodge 2500 5.9 Cummins
    Husky 372xp
    Husky 55 Rancher
    Maruyama trimmer
    Husky trimmer
    Redmax BP blower
    Toro zero turn
    North Star 4 K PSI pressure washer
    Honda 300 4 trax
    Yamaha Timberwolf
    liquid logic coupe kayak
    16' Tow Master Dump Trailer ,20' Yanmar Hauler

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