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Old 08-27-2018, 09:08 PM   #1
scottz
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Air Conditioning Problem Found - Maybe

Background: I have been having a problem with the bedroom AC unit (occasionally the main room unit, but mostly the bedroom) when run in auto mode. It will occasionally shut off; I suspect it is freezing up (getting large amounts of water off the front roof). We would notice that the unit was not running (normal in auto mode) and it was getting warm in the room. Checking the temperature revealed that it was much warmer in the room than the thermostat set point. Turn the unit off/on and it would start running. When the unit runs, it runs perfect. The work-around is to leave the fan in high mode; the room stays at the proper temperature.

Dometic suggested I replace the thermostats; did that, no help.

I took it to a dealer, and after a couple hundred dollars testing, they told me they could not get the unit to shut down and that the inlet/outlet temperatures were within specs. Of course I told them that before ever taking it in; my fault for thinking they would be helpful.

I got around to looking at it a few days ago. I pulled the unit off the roof (easy, four bolts) to take a look. I was thinking I might find an issue in the roof plenum between the cold air side and the return side, but it looked good. Just for good measure I re-taped the ducts and was getting ready to put it back together when I noticed something. The bottom of the air conditioner is sealed to the roof with foam insulation; I suspect installed on the AC unit at the Dometic factory. There is a strip around the outside of the of both holes and another strip between the cold side and return side. Measuring the center strip, I found that Keystone did not center the AC unit over the cutouts. The center strip was 2" forward of the part of the roof it was supposed to seal against; leaving about a 3/4" opening where the cold air output could go directly into the return air duct (photos 1 & 2). The fix was simple, relocate the foam piece so it would seal against the roof (as opposed to moving the whole AC unit back 2") (photos 3 & 4).

After putting it all back together, I ran the unit for three days without a shutdown. I am not ready to call the problem solved because it is not very hot or humid here; time will tell. If it does continue shutting down, I'm ready to give up and run it in high mode all the time.
Attached Images
File Type: jpg 2018-08-22 17.55.25 -2.jpg (1.26 MB, 48 views)
File Type: jpg 2018-08-22 17.55.43 -2.jpg (1.31 MB, 32 views)
File Type: jpg 2018-08-22 17.57.55 -2.jpg (1.11 MB, 26 views)
File Type: jpg 2018-08-22 18.03.51 -2.jpg (1.00 MB, 25 views)
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Old 08-27-2018, 09:11 PM   #2
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M.O.C. #19755
Here is what the roof cutouts look like; before and after the re-tape job.
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File Type: jpg 2018-08-22 14.59.23 -2.jpg (1.14 MB, 34 views)
File Type: jpg 2018-08-22 17.07.27 -2.jpg (1.54 MB, 27 views)
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Old 08-27-2018, 09:50 PM   #3
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Nice job and a common problem, my dealer did that under warranty and said they would be checking all of them coming in from then on. Since, like us, you have a 2017 you should also check your return air ducts. On ours the ducts were cardboard and collapsed. I put two 9" lengths of 11/2" PVC pipe lnto each side of each one and opened that up. I also cut half the fins off of 5 of the supply ducts and shortened the shaft to match the ducts on all of them to increase the air flow.
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Old 10-24-2018, 01:32 AM   #4
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I worked up the energy today to pull the rear AC off and take a look at it. Same problem as the front. The unit was not aligned with the holes in the roof; it was about 1 3/4" too far forward. I had to re-position it to get all the gaskets to line up.

I found an easy way to check for this problem without pulling the unit off the roof. Pull the cover off, then pull off the foam that covers the squirrel cage blower and duct work. You can put your hand down and feel if the seals of the cold side and return side match the holes in the roof and proceed from there.

Photo 1 shows how the unit was misaligned (and after I re-taped the duct work). The blue tape closest to the camera is where the seals were; the blue tape closest to the cutouts is where the seals should be.

Photo 2 is shows the cutouts and the bottom of the AC unit.

Photo 3 shows the top of the AC unit with the foam cover removed. You can see the cold air duct below the squirrel cage blower; the return duct has all the wiring in it.

Photo 4 shows how far I had to move it. I used a little Dicor to seal up the old holes.

One note of caution: If you pull the AC unit off the roof, do not over torque the bolts when putting it back on. The roof of the RV is curved, the bottom of the AC unit is not. If you over torque the hold down bolts, the housing will distort and the top cover will not fit properly. I had to loosen the bolts a little to make everything fit right. I ended up torquing them just enough to compress the foam about half the distance between when the foam touches the roof and the bottom plastic pan of the AC unit. Hope that makes sense.

One has to wonder why it is so hard to align these things at the plant.
Attached Images
File Type: jpg 2018-10-22 17.19.17 -2.jpg (1.40 MB, 23 views)
File Type: jpg 2018-10-22 17.24.42 -2.jpg (1.10 MB, 24 views)
File Type: jpg 2018-10-22 18.07.55 -2.jpg (1.33 MB, 27 views)
File Type: jpg 2018-10-22 18.02.22 -2.jpg (1,014.8 KB, 23 views)
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Old 11-03-2018, 07:31 AM   #5
Denny and Angie Miller
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Nice job! Thanks for sharing and including photos.
With photos in hand, I would let the dealer know I expect (at least a partial) refund on the previous testing. I know, don't hold my breath....I would at least get some satisfaction letting the service manager know the owner was able to find the problem when his techs could not.
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Old 11-11-2018, 12:42 AM   #6
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Quote:
Originally Posted by Denny and Angie Miller View Post
Nice job! Thanks for sharing and including photos.
With photos in hand, I would let the dealer know I expect (at least a partial) refund on the previous testing. I know, don't hold my breath....I would at least get some satisfaction letting the service manager know the owner was able to find the problem when his techs could not.
I would if it was not a 6 hour drive each way; not worth the effort.
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Old 09-08-2019, 08:20 AM   #7
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Yet another AC mis-install

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Originally Posted by DQDick View Post
Nice job and a common problem, my dealer did that under warranty and said they would be checking all of them coming in from then on. Since, like us, you have a 2017 you should also check your return air ducts. On ours the ducts were cardboard and collapsed. I put two 9" lengths of 11/2" PVC pipe lnto each side of each one and opened that up. I also cut half the fins off of 5 of the supply ducts and shortened the shaft to match the ducts on all of them to increase the air flow.

Thank you all for posting these. I pulled my front AC off this weekend and found the same issue. My return duct legs on both sides were also nearly closed where they join the distribution box. Taped everything up like I actually cared what it looked like (like the factory should have), and pushed through the PVC pipe from the top. Now, the AC works. Amazing how the dealer (CW) never found this after I had it in twice under warranty for this.
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Old 09-08-2019, 09:22 AM   #8
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Fantastic job! do you think that Keystone will be doing a recall and addressing this on all the AC's or am I being naive?
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Old 09-08-2019, 11:28 AM   #9
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Yes and Yes!
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Old 09-08-2019, 01:44 PM   #10
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Really good post with the pics included. I must say that many of the owners on here would be better repair guys than the idiots at the dealerships!!!


But, no one should be surprised that the so called "Techs" at a sales dealership would be able to figure out much of anything. They are more or less there to fix minor cosmetic issues to get the units off the lot!!


If you want repair work done right go to a REPAIR ONLY shop! There business model is based on actually fixing problems correctly the first time and as fast as possible. Heck even a mobile service tech is better than 99% of the sales dealership techs......
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Old 09-08-2019, 07:09 PM   #11
cmccuan
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We had those same issues. How on earth do you install on the wrong place. In addition ok ducts were crushed during construction. Keystone said to instal hot tub tubing to open it up. It did the trick, but we have to keep in on high. Same as 2 of the other 3 Rvs we've owned. I guess it's a thing...��
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Old 09-14-2019, 08:53 PM   #12
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I don't know. It shouldn't be a thing. My first trailer was a Jayco Pop-up in the 80's (and it was probably 20 years old when we bought it), then I had a Wilderness and then a Terry, both Fleetwood (before the 2009 restructure) products. Those Fleetwoods were bulletproof. Great fit, finish, appliances, etc. They each gave us over 8 years faithful service. If Fleetwood was still in business making trailers, I'd have bought another one. Don't understand why the Montana is so poorly assembled. I supposed there are people out there who don't have problems.
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Old 09-15-2019, 07:29 AM   #13
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Agree, shouldn't be a thing, but like I said, we're on our 4th RV. All different. The best one was a 2002 Newmar Kountry Star 5th wheel. They don't make them anymore...��
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Old 09-15-2019, 09:01 AM   #14
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Really appreciate this info. I have the exact same issue (among others) on my 2019 3731. One question is what does "collapsed" mean on the duct-work. I took off a vent cover and there was about 1.5 inches of space, but I could push up the top part of the duct another inch or so. I am in Texas and have never been able to get the inside temp below about 78 in the hottest part of the day in the summer. "Auto" wont cut it and have run on High to have any change of cooling. Already have new thermostats and dealer gave me the working as designed speech, and wanting to sell me a 3rd AC unit, which might be a good idea.
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Old 09-15-2019, 09:35 AM   #15
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The tech, a real wiz in Saratoga Springs NY. Checked the air flow, not just the temp of air. Said it was not sufficient. Never saw reading myself, but felt like he knew that even if it was, itcwasnt cutting it. It seems that during construction the ducts were crushed enough to limit air flow in all but one duct. Keystones "fix" was to put clear sturdy hot tub hose in there to open it up. Hose was standard size I've seen on our hot tub but don't know actual dimensions. Probably, 2-2 1/2" my husband guesses. He carefully stuck about 3' in each vent using his hand and the length of his arm to make sure it went in smoothly. It's worked fine on "high" when it's 85 degrees and more and "auto when lower temps outside. Has a differential step down of 15-20 degrees. I think if we weren't under warrenty and knew about this we could have done it ourselves.
Also, need to mention, without any equipment I could tell the air coming from the vents was not forceful enough.
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Old 09-15-2019, 10:38 AM   #16
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Collapsed Vents

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Originally Posted by cghsatx View Post
Really appreciate this info. I have the exact same issue (among others) on my 2019 3731. One question is what does "collapsed" mean on the duct-work. I took off a vent cover and there was about 1.5 inches of space, but I could push up the top part of the duct another inch or so. I am in Texas and have never been able to get the inside temp below about 78 in the hottest part of the day in the summer. "Auto" wont cut it and have run on High to have any change of cooling. Already have new thermostats and dealer gave me the working as designed speech, and wanting to sell me a 3rd AC unit, which might be a good idea.
The issue is the returns are collapsed. I don't think my supply duct is. If you pull those covers and the foam filter and stick your hand inside, mine I could barely get my fingers through. Most folks have used 1.5" PVC pipe sections. I used 1.25 and they were touch to work in without damaging the duct. 2' on either side of the rooftop unit is all you need, a coupler, and install them in 12" sections at a time. I went from the roof and had to pull my units (easy to do). There was another post in this forum where the guy found that Keystone didn't align the units over the supply and return box properly. Mine was the same so I ended up opening the return side as 1/2 of it was blocked. It is all within the seal on the bottom of the Dometic, so no leak problems and I didn't have to make new mounting holes. It's easy to install the PVC from the roof on the 3820FK as there's plenty of room. The other thing that people have found is the supply air diffusers are restrictive. That is true. I've pulled all mine off and just have open holes waiting for the new ones to arrive.
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Old 09-15-2019, 10:50 AM   #17
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Quote:
Originally Posted by cghsatx View Post
Really appreciate this info. I have the exact same issue (among others) on my 2019 3731. One question is what does "collapsed" mean on the duct-work. I took off a vent cover and there was about 1.5 inches of space, but I could push up the top part of the duct another inch or so. I am in Texas and have never been able to get the inside temp below about 78 in the hottest part of the day in the summer. "Auto" wont cut it and have run on High to have any change of cooling. Already have new thermostats and dealer gave me the working as designed speech, and wanting to sell me a 3rd AC unit, which might be a good idea.
Just thinking about this - supposedly Keystone fixed the collapsed duct problem on late 2017 builds going forward. Yours is new so I'd park it at the dealer until it's right. Just for comparison, with the fixes to mine, I can get the interior down to 76 in full sun on a 92 degree day, fans on high, under 30% humidity. Before the fix, 85 was the coolest I could get. That's with both running.
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Old 09-23-2019, 04:34 PM   #18
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Originally Posted by Our3820FK View Post
Fantastic job! do you think that Keystone will be doing a recall and addressing this on all the AC's or am I being naive?
Are you kidding!!!
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Old 09-23-2019, 06:46 PM   #19
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I tried to get them to take it back! (Silly , ..i know...) The dealer offered to buy it back at a 20% loss for me, but I was so angry I wouldn't even consider it.
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