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Roof gasket on rv a/c

When I replace roof gasket on my rv air conditioner, is there a set amount of torque when tightening mounting bolts?

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Mike Butler

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Try not to compress gasket past 1/2 it's original thickness. Most of the factory ones have tabs that stick down, and supposedly when they touch the roof, it's far enough, which is about same as 1/2. I use my cordless with the torque setting on it, at about 2-3 until I see how far that draws down, then increase/decrease as needed from there.Once i feel it's 1/2 way, I torque all at same setting on drill to make sure all equal.

Posted on Aug 15, 2008


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How to replace rv roof ac?

I will assume that you are aware of the fact that both upper ( unit on roof ) and lower control unit ( inside at ceiling ) will need to be replaced. That obviously adds to cost, instead of just replacing upper unit with same as what's there. Be sure to shut power off at breaker panel to start with. There is only 4 bolts, usually 1/4" with either 3/8" or 7/16" head, That holds the upper to lower. Once you remove them, and any extra screws that may go into ceiling from lower unit, the 2 pieces are separate. Disconnect any wiring ( mark wires if thermostatically operated) from lower unit, and if it's not ducted in the ceiling there will be ducting attached from upper to lower unit usually with flanges that have screws in them. 3 Philips screws where it attaches at base of upper unit, and that should drop down. That should be it. Now just lift unit on roof up and off. May take a bit off effort as some stick pretty good. Be sure to watch if you have a rubber roof that the rubber isn't ripping. I have had some that the person who installed it used some sealant at gasket surface, and had to very carefully lift and pry it apart, but as I said, if you find same, watch rubber for ripping. No need to apply anything to gasket if roof is clean, just set new one down over hole, even it up and draw down from inside with new ceiling assembly and bolts equally. Only compress gasket to approx 1/2 it's original thickness when tightening down, do not squish it.

Mar 03, 2012 | Dometic Rooftop RV Air Conditioner

1 Answer

Our penquin dometic air conditioner in the bedroom pours leaks lots of water when the unit is on during rain storms. Water leaks into the ceiling and also out the unit.

Sounds like base gasket at roof is loose or defective to start with. Try removing ceiling assembly enough to tighten 4 bolts that secure roof unit to inside bracket. Do not compress too much, just snug them all evenly and see if water slows or stops. If not, you will have to remove upper unit (roof) and replace gasket and re-secure but don't tighten to excessive, only compress gasket approx half of original thickness. Also make sure upper unit is aligned properly with opening of roof.

Sep 23, 2011 | Dometic Rooftop RV Air Conditioner

1 Answer

RV AC is working fine, but the water is leaking from the ceiling Where is the drain tube on the unit, The AC unit is a roof type, Duo Therm serial # 43404934, Part # 3105459

Normally, the condensate will drain out of the unit onto the roof and off the edge to the ground. Remove your cover inside (probably 2 screws) and tighten the 4 bolts you will find inside. If they are tight, go to your RV supply place and get new roof gasket. Remove the AC and insert the new gasket and resecure the AC to your roof.

Thanks for your question @

Jul 26, 2011 | Dometic Rooftop RV Air Conditioner

1 Answer

I purchased a 2008 sprinter in the US I have water comming in through the roof heat/air unit when it rains what could the possible solutions be I have no warranty in Canada there is little resistsnce it...

Remove the ceiling assembly enough to look for 4 bolts that secure upper unit to roof. Will be 4 bolts or studs with nuts,one at each corner of the opening in roof. Look up inside to make sure gasket is aligned all around the 14" square hole, then tighten down until gasket is compressed good, but not too tight. ( Gasket should be tightened down to point that it is compressed to approx 1/2 it's original thickness.)
Visually inspect and feel gasket area when you have ceiling assembly down to make sure it's clean and no debris stuck under gasket as well.

Jun 25, 2011 | Dometic Rooftop RV Air Conditioner

1 Answer

Help. Just had seal replaced now water flows in rather than leak. Of course the place that did the repair is hundreds of miles away. How do I tighten seal?

It could be that the installer did not tighten the mounting bolts sufficiently to make a seal. Taking the cover off the unit inside the coach, you should be able to see four mounting bolts that are inserted through springs between their heads and the ac unit.

Those mounting bolts are what pulls the AC unit snug against the gasket. The instructions say not to overtighten them when you first install them because you need to leave space to tighten them later as the gasket ages and loses its "spring". The gasket also, over time, compresses under the weight of the AC sitting on the roof "bouncing" as you drive down the road, losing the seal.

So that you have room to tighten them later, the springs on those mounting bolts should not be compressed all the way. However the bolts also need to be snug enough initially to make the seal and not just barely threaded in. You should not compress the gasket more than 50% on initial install, but it should be compressed a bit.

Try tightening them a bit with a socket wrench (tighten all 4 to an equal depth), then spray the roof area around the AC with a garden hose to see if you still have the leak.

Jun 20, 2010 | Dometic Rooftop RV Air Conditioner

1 Answer

How do you fix seal leak on dometic rooftop air conditioner ?

remove filter etc. from ceiling assy, you'll see 4 bolts that you remove,(basically 4 corners of lower tray at ceiling) unplug wiring harness and connector, that goes to upper unit from lower, then lift upper unit up off roof. position upper unit to allow for removal of 14" gasket. Install new gasket, set upper unit back over hole align properly, and re-install 4 bolts. Snug evenly until gasket is approx. half thickness of original. Re-attach harness plug etc.

May 06, 2010 | Dometic Rooftop RV Air Conditioner

1 Answer

How to properly install roof top ac

What make and Model? You basically set it over framed 14"x14" hole, with clean surface, align it properly so gasket is aligned all around hole, install ceiling assy, inside with 4 bolts that extend to unit on roof, and draw it down evenly until gasket is compressed about 1/2 it's original thickness, hook up your wiring, etc. Are you starting from scratch, or replacing another unit?

Mar 17, 2010 | Dometic Rooftop RV Air Conditioner

1 Answer

Water leak where is the foam gasket on the roof

Depending on the age of your unit there are 4 or 6 screws holding the ceiling unit up to the ceiling.
Unlatch the black plastic screws by turning them 1/4 turn and drop down the center filter panel.
This will expose the mounting screws which again depending on the age of your unit may or may not be spring loaded. If they are spring loaded there will be 2 extra screws one on each side.
As you drop the plenium down be careful of the wiring
There are 4 8" long bolts that hold the upper A/C unit to the roof via a metal bracket under the ceiling.
We always use a cordless screw driver with a clutch in it to insure that we torque each bolt evenly in a cross corner pattern. You can tighten these bolts pretty darn tight
This should solve your leak if it does not you may have to remove the upper unit and replace the gasket which should be available from any good RV shop
Total time required about an hour

Mar 07, 2010 | Coleman Mach 15 Air Conditioner

1 Answer

How to remove the complete roof top ac unit , 1980 GMC Tioga RV

Shut off Any AC power (hydro) to it, remove ceiling assy (inside part) and you'll see 4 bolts going up through lower assy, and into base of upper assy (roof unit) . Remove those 4 bolts and any wiring harness connected from lower to upper unit. Lift it off. If your just replacing the upper assy, leave hydro wires hooked up to lower assy , and let it hang, while you clean surface on roof for new install. Re-install 4 bolts and tighten equally until gasket is approx 1/2 thickness it was before tightening. Re-install wiring harness plug in to lower unit etc. If not replacing, but removing entire assy (upper and lower) be sure to Marette and tape hydro wires as well as any 12 volt wires, and tuck away safely. Install a vent on current opening , or whatever you choose.

Sep 28, 2009 | Dometic Rooftop RV Air Conditioner

2 Answers

I have a leak and it does not seem to the be the new gasket

They say you should only compress the gasket to approximately 1/2 it's original thickness, and sometimes there are tabs that touch roof to tell you that's far enough. If your sure it's coming in around gasket where it meets roof, try loosening bolts off to allow you to lift upper unit off roof enough to use a caulking gun with a tube of "dicor" self leveling sealant, and run a bead of Dicor around where gasket meets roof , then set unit back down, & tighten until gasket is about 1/2 thickness as new.I always find it better to remove bolts & flip unit on it's side and get good bead down center of where gasket meets roof, then set unit back down, line it up & snug it down.Let it sit for a while to set a bit. Be ready with a rag to catch or wipe any excess that squeezes out from under gasket to the inside, that may end up on floor below, as it's very hard to remove that stuff after the fact.Has worked for me in similar situations.

Jul 01, 2009 | Dometic Rooftop RV Air Conditioner

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