Fitting rooftop ac gasket (Dometic)

Discussion in 'Heating / Cooling Systems' started by skeetercampsintexas, Mar 17, 2013.

  1. skeetercampsintexas

    skeetercampsintexas Active Member

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    So a good while back I posted a thread about my rooftop air conditioner leaking water into our camper through the vents. Well I boiled this issue down to the gasket being the problem. Some people say to remove the fascia inside the camper and tighten the four bolts a bit more to get a little more life out of the gasket. Let me say this....don't do that!! These gaskets are less than $30 and by tightening the bolts more you are literally forcing water into the wood frame that's under your AC. This is the issue I ran into. First off the AC was easy to remove. Take off the fascia and disconnect the wiring. Next step is to loosen the four bolts around the corners of the AC. At the point you are ready to remove from the roof. I did all of this by cranking the roof up about 2 feet or so that way I had room to work inside and easy access to the rooftop without a ladder. By the way removing the unit from the rooftop is NOT a one man job. Don't worry about breaking bolts, they're easy to replace. The old gasket came off and lo and behold the prior owner had performed this tighten up the bolts trick and ALL of the wood frame was completely rotten almost as if we had termites! So I went to the hardware store and got some lumber, liquid nails, and silicone gasket maker from the auto parts store. The new gasket was only $23. I cut the wood framing and dry fit it to check for any issues. All was OK. At this point make sure you have help ready and all parts available in a flash because the next few steps MUST BE DONE QUICKLY! Next thing is to apply liquid nails to both sides of the frame, have your gasket already on the bottom of the AC, it comes with a sticky side to apply. After the liquid nails insert your wood between the roof and ceiling. Next apply a generous line of silicone gasket maker to the ROOF to serve as another seal against the elements ( be sure to have a clean working surface first). Then have your helper and yourself set the ac down and go back inside and tighten the 4 bolts. Not too tight just enough to slightly squeeze the gasket. Then hook your electrical back up and install the fascia. You're done! This was one trip to home depot and about 3 hours of work. After a good test run I've got no more leaks! For those of you with any questions feel free to ask. And for those who read my other thread with no reply from me, my sincere apologies but I got lazy and was busy growing a moustache or something like that lol but this was a"round-to" job and you know what? I finally got round-to it lol
     
    Wanderlust67 likes this.
  2. jeeper88

    jeeper88 Let's go Camping and Jeepin

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    Nice write up. I have marked this one for future reference.
     
  3. Xolthrax

    Xolthrax Franconia, Pa.

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    Good advice. Better to do the job right.
     
  4. fmbhappycamper

    fmbhappycamper PuP Power

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    I just re caulked the roof and am ready to paint with rubber roof, I don't have leaks from the AC and did not want to deal w/it, was gonna paint around the AC but now I may remove it and get a new gasket, Thanks [8D]
     
  5. skeetercampsintexas

    skeetercampsintexas Active Member

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    Yeah in all honesty I tackled the job not know what I was in for! I'm a mechanic by trade so by no means was I scared of it however air conditioning aside from on vehicles is not my job. After getting things off to a start I realized it was not at all a difficult repair. Granted you need some help but I'm sure a good buddy and a 6 pack will take care of that. I've heard that in place of using silicone gasket maker you can also use wheel bearing grease, however as a mechanic I'm a huge fan of gasket maker [;)] best of luck to all of you if you tackle this task and you'll find out just as I did its well worth doing it yourself. I didn't even take the cover off the AC! Lol!
     
  6. scsteven

    scsteven New Member

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    We need to do this to our camper. Where did you get the new gasket from?

    Sent from my GT-N8013 using Tapatalk HD
     
  7. billangiep

    billangiep Member

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  8. scsteven

    scsteven New Member

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    Thank you!

    Sent from my GT-N8013 using Tapatalk HD
     
  9. tconroy

    tconroy Active Member

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    thanks for posting this info. I need to do this and didnt know if you had to lower the roof down completely after taking things loose inside. I have a sink that has to flip so I think I can get the 2 feet I need to get on the roof after loosening up the inside bolts. the dealer told me I could change it from the inside. Dont know how that could happen if you have to physically remove the ac unit. My question is did you put some plywood down to get on the roof to spread out the weight of you being up there or what????
     
  10. friartuck

    friartuck Well-Known Member

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    I just did mine this past weekend. I had a friend who has done this before help [:D] We used plywood on the roof between the edges, where we were leaning our elbows (and bellys) to spread the load on the Flion roof. We used a sturdy piece of cardboard to put the AC on when it came off. I did lower the roof till it was resting on the , slightly extended bunkends. So it was supported besides the cables. I think it is a good idea to at least check the trim piece, mine was loose on two side. The protective covering for the butyl tape had never been removed so those two side never 'stuck' to the roof! We also found a 6" crack leading out from a corner. We were able to fiberglass a patch on and the shroud hides most of the off color paint.
    A couple of beaks of good exterior flexable caulk and the trim piece went on, gasket on the AC unit and everything back in place. Really a very easy job.
    Amazon had the gaskets for I think $17.00 dollars, maybe 20. DW ordered some books to make the 'free shipping' amount anyway. [:D]
     
  11. tconroy

    tconroy Active Member

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    im doing mine tomorrow but it looks like PO put a small bead of caulk under the gasket for whatever reason. Dont know if I should or not.
     
  12. bondebond

    bondebond New Member

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    Do NOT use caulk of any sort in the application of the gasket.

    They will come with an adhesive strip on one side. This adhesive side goes onto the bottom of the A/C pan itself and is solely to hold the gasket in the proper place during placement of the A/C back over the hole. The gasket should be allowed to have direct contact with the roof of the PUP. Adding caulking either under it or on it afterwards is prone to failure due to the flexibility and compressible nature of the gasket itself.

    It is conceivable and useful to tighten the bolts up over time as this gasket will slowly compress over its useful lifetime. There comes a point, though, when it is time to change it out. For me, that is when it is between 1/2 and 1/3 of the original height.

    Clean the roof around the opening so the new gasket rests on a clean surface, place the A/C, install and tighten the four bolts inside to draw the A/C towards the mounting bracket/control panel.

    While everything is still in this condition, use a hose and mild pressure from it aimed at the gasket. I mean quite modest pressure. Check the inside for leaks. This should help identify if you have the gasket properly placed and compressed.
     
  13. jerdude

    jerdude Like camping, hate setting up and breaking down

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    I will reiterate in my own words to make sure I have the process correct, OK?
    Gasket for A/C unit is generic, may be purchase on Amazon.
    BUTT, were do I get the information, under ceiling piece?
    Raise pup roof 2 feet,
    Crawl in and remove inside cover of A/C
    Loosen 4 securing bolts (one each corner) to allow A/C unit on roof to be removed.
    Buy 6-pack, call buddy and plead to come help juggle the A/C Unit off bolts.
    Have wood spanning roof side to side to disseminate weight of A/C on roof.
    Clean and scrap old remains off roof, re-clean surface to adhere new gasket.
    Question: did you clean the bottom of the A/C ? IF so how?
    Put A/C back on bolts with new gasket in place, clear work materials off roof.
    Climb down and tighten bolts 1/4 turn past snug,
    Lower roof.
    Test with slow stream of water,
    No leaks put inside piece back up on ceiling.
    If leaks show tighten bolts another turn if leaks appear.
    [;)]
    When done, crack open the 6-pack with bud, thanking him purfusely .
    Did I miss anything?? :)
    Thank YOU, very much for the instructions, thought I had an exploded diagram but I cannot find the damn thing. [:(!]
     
  14. COdreaming

    COdreaming New Member

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    Most A/C gaskets are 14". I'd be shocked if yours is bigger.

    I'd remove the four bolts, not loosen them. The roof unit is going no where!
    With the bolts removed, you won't have to jiggle anything! [8D]

    I used a scrapper to remove my gasket from the bottom of the A/C pan.

    Make sure you apply the gasket to the bottom of the A/C unit, NOT the roof.

    Tighten the bolts until the gasket is compressed 1/4 total thickness. The bolts will never be "tight" until you've tightened it too much and you've fully compressed the gasket (big no-no). [:O]

    It's actually really easy. The hardest parts are getting the thing off the roof and screwing the bolts on from the inside of the trailer!

    Good luck!
     
  15. jerdude

    jerdude Like camping, hate setting up and breaking down

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    Thanks for the look over on my directions COdreaming.

    This is silly to ask, but how do you know the hieght is 1/4" down?

    Is the thickness of the new gasket that obvious.

    Thanks,
     
  16. tconroy

    tconroy Active Member

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    I hand tight end mine in the front first then the back didn't need a wrench. The back is heavier than the front. Whatever you do don't crank on it.
     
  17. COdreaming

    COdreaming New Member

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    You eyeball it. Don't go by measurements, at least I don't. Once you set the A/C on the roof, you'll be able to see the gasket through the opening inside the camper. Just start tightening down until it looks like the gasket has compressed 1/4 of the way down.


    Sent from my iPhone using Tapatalk - now Free
     
  18. scsteven

    scsteven New Member

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    Thought I'd report back that the seal replacement went great and all is good!! Thanks for the help!

    Sent from my GT-N8013 using Tapatalk 4
     
  19. tconroy

    tconroy Active Member

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    good to hear that. I turned mine on after replacing and had a small leak in the front, 1/2 turn on the bolt and all is good. I did notice the back is heavier that the front on the AC. Not really balanced over the hole so the back was compressed more already. After running it I take the filter cover off and use an inspection mirror and my phone flashlight to look around the gasket for leaks. Just paranoid I guess
     
  20. banks412

    banks412 New Member

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    Can someone advise me on how to attach pics to posts? When I click on the insert image button, I get /[IMG]. I'm guessing I Need to somehow insert the picture between those, but what do I do? Excuse my ignorance, but I'd like to post some pics and get y'alls and the OP's advice on a similar situation.
    Thanks!
    Tim
     

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