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Old 08-08-2021, 02:44 AM   #1
DonnaN
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Alpine 3790 a/c issues

We purchased a 2021 3790 fk and can’t get the dealer to help with a/c issues. Service says 5 degree difference between set temp and actual temp. Both a/cc’s are on auto. Either they cycle on and off all the time or we have to power off to reset. Got up this morning and condensation and water all over every a/c vent. Have 2 dehumidifiers running and both were full. Any ideas on what to do? Service tech said issues with the alpine and high country. Turn off auto and put on cool high fan. Must be a different solution.
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Old 08-08-2021, 03:39 AM   #2
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Quote:
Originally Posted by DonnaN View Post
We purchased a 2021 3790 fk and can’t get the dealer to help with a/c issues. Service says 5 degree difference between set temp and actual temp. Both a/cc’s are on auto. Either they cycle on and off all the time or we have to power off to reset. Got up this morning and condensation and water all over every a/c vent. Have 2 dehumidifiers running and both were full. Any ideas on what to do? Service tech said issues with the alpine and high country. Turn off auto and put on cool high fan. Must be a different solution.
Running two dehumidifiers inside a sealed trailer is also producing some heat.
The dry air can be warmer causing an additional albeit drier heat load
The ac unit sounds like it’s froze now from running constantly.
There are posts on here about improving air flow and sealing all of your ducts with hvac foil tape..do a site search or look through the forum under repairs/ maintenance column and read any hvac related posts.
Member Javi just upgraded to a 15000 btu ac unit in his bedroom I believe and posted good results.. think he has a avalanche fifth
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Old 08-08-2021, 04:25 AM   #3
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Quote:
Originally Posted by DonnaN View Post
We purchased a 2021 3790 fk and can’t get the dealer to help with a/c issues. Service says 5 degree difference between set temp and actual temp. Both a/cc’s are on auto. Either they cycle on and off all the time or we have to power off to reset. Got up this morning and condensation and water all over every a/c vent. Have 2 dehumidifiers running and both were full. Any ideas on what to do? Service tech said issues with the alpine and high country. Turn off auto and put on cool high fan. Must be a different solution.
We have the same 5er have the same problem but, only with the Bedroom AC. No issues with humidity though.I sometimes have to put it Fan/High mode for around 10 seconds then back to Cool/Auto mode to get it to run, other times it runs when the set temp is higher then the temp at the temp sensor at least when I check it with one of those laser temp guns. We are on the road until early November so we are just dealing with it until we get back home and I can get it to the dealer.
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Old 08-08-2021, 05:21 AM   #4
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Every 2021 Alpine is having the same issues... You need to remove the roof A/C units and open up the ductwork... The factory over used spray foam during their seal work and blocked off better than half of the ducts open area... See image of foam mess

Also you need to remove the overhead A/C return grills and open up the under cut area to match the grill width so the A/C units can breath

Next remove every overhead Duct and retape the lousy HVAC tape around each overhead cutout

Also remove the remote temp sensor covers and verify the sensor is mounted outside the wall.. if its stuck inside the wall, as many are the sensor cant read ambient room air temp

The info I've posted here is FACT... I am in a dedicated Alpine group and the images are from owners of new Alpines with the Dometic NXT series units installed... The workmanship currently coming out of the Keystone Alpine division is NOT what it was 5 years ago...

And my 2014 Alpine had "some" issues .... but noting like what we are seeing right now with the new builds
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Old 08-08-2021, 05:30 AM   #5
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Avalanches are having many of the same problems... We spent two days re-taping the registers and cleaning up and re-taping the intakes for both the front and rear A/C in mine.. and because we saw the mess in the duct work when we replaced the bad front A/C we also pulled the rear unit and re-taped and cleaned up the sorry job the factory did...

Cost me some cash out of pocket but it was well worth the cost..

I chose not to buy the Alpine because of the In Command system
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Old 08-08-2021, 05:48 AM   #6
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Originally Posted by ChuckS View Post
Every 2021 Alpine is having the same issues... You need to remove the roof A/C units and open up the ductwork... The factory over used spray foam during their seal work and blocked off better than half of the ducts open area... See image of foam mess

Also you need to remove the overhead A/C return grills and open up the under cut area to match the grill width so the A/C units can breath

Next remove every overhead Duct and retape the lousy HVAC tape around each overhead cutout

Also remove the remote temp sensor covers and verify the sensor is mounted outside the wall.. if its stuck inside the wall, as many are the sensor cant read ambient room air temp

The info I've posted here is FACT... I am in a dedicated Alpine group and the images are from owners of new Alpines with the Dometic NXT series units installed... The workmanship currently coming out of the Keystone Alpine division is NOT what it was 5 years ago...

And my 2014 Alpine had "some" issues .... but noting like what we are seeing right now with the new builds
The other day I re-taped all the overhead ducts. My returns all look pretty good. I will check the temp sensors positioning. Opening up the rooftop ducts will have to wait until I get home. Thanks again Chuck for all the info you provide.
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Old 08-08-2021, 08:23 AM   #7
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Two images of roof A/C with styrofoam cover removed to allow access to evap coil amd gateway box… first 8mage shows zero HVAC tape to seal the edges of the ductwork.

Second shows what the OP did to clean up the leftover mess from factory and seal the duct edge with HVAC tape as well as reposition wire harness out of the duct passageway

This is also on a late model Alpine. You can see all the crap that’s sucked into evap coil…

This is left over crap from the factory during assembly that should have been cleaned out before putting the covers on

And this is not just Keystone… it’s ALL RV builders right now. Not much in the way of QC during assy
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Old 08-08-2021, 09:01 AM   #8
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Quote:
Originally Posted by ChuckS View Post
Every 2021 Alpine is having the same issues... You need to remove the roof A/C units and open up the ductwork... The factory over used spray foam during their seal work and blocked off better than half of the ducts open area... See image of foam mess

Also you need to remove the overhead A/C return grills and open up the under cut area to match the grill width so the A/C units can breath

Next remove every overhead Duct and retape the lousy HVAC tape around each overhead cutout

Also remove the remote temp sensor covers and verify the sensor is mounted outside the wall.. if its stuck inside the wall, as many are the sensor cant read ambient room air temp

The info I've posted here is FACT... I am in a dedicated Alpine group and the images are from owners of new Alpines with the Dometic NXT series units installed... The workmanship currently coming out of the Keystone Alpine division is NOT what it was 5 years ago...

And my 2014 Alpine had "some" issues .... but noting like what we are seeing right now with the new builds

The use of the expanding void filling foam can be intoxicating fun! I used it to fill voids in my camper where mice could get in and after I finished I found voids all over that just had to be filled... never got the hang of how long to fill and all expanded into mountains of dried foam. It seems difficult to get rid of once applied, btw...
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Old 08-08-2021, 09:43 AM   #9
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From a 2021 Alpine.. the OP is on his roof now and has removed one of the A/C units and this is what was blocking his airflow…
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Old 08-08-2021, 09:44 AM   #10
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Originally Posted by wiredgeorge View Post
The use of the expanding void filling foam can be intoxicating fun! I used it to fill voids in my camper where mice could get in and after I finished I found voids all over that just had to be filled... never got the hang of how long to fill and all expanded into mountains of dried foam. It seems difficult to get rid of once applied, btw...
Not only is it "intoxicatingly fun" but it also has a potential to "make things worse as it expands"... Apply a tad too much and as it "grows to fill the void" it can (and often does) push what was "no gaps in the material" causing those well sealed areas to "open up from the expanding foam"....

So, not only is this a product where "enough is often too much" but it'll do it's expanding after you're finished, making "once weather-tight and water proof seams" open up and become an extension of what you were trying to close.....

Use expanding foam "judiciously"....

I once had a "well bowed bathroom wall" in a house that I thought could use more insulation on that "chilly outside wall under the window over the toilet"... We lost about 3" of width in the bathroom and every time I sat on the toilet, my knee hit the TP holder.... Expanding foam is "exactly that" EXPANDING .......
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Old 08-08-2021, 09:47 AM   #11
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This is his redo on the OEM duct on the roof… he just fired up the A/C and states it is world of a difference in airflow coming out the inside vents now
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Old 02-26-2023, 07:54 AM   #12
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Foam everywhere!

So we recently purchased a "New" 2021 Alpine 3790FK from a guy that bought it to live in while he built a house. He never ended up using it and it sat on a pad, under a pole barn, hooked to power for a year. It was never used other than running the slides and "hanging out" for the day every month or so. Needless to say, we got a great deal. As with all rigs, we are fixing all the manufacturer mistakes but for the most part this rig seems to be well put together. The weather is warming up here in the panhandle of Florida and the AC volume and cooling just wasn't right. After reading through this thread I decided to yank the roof units and investigate....WOW!!!
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Old 02-26-2023, 07:55 AM   #13
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After removing foam.

Pic after removing foam and foil tape.
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Old 02-26-2023, 07:58 AM   #14
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Air box reworked with Kilmat!

Reworked the box with Kilmat which serves two purposes, seals the box tight and absorbs a lot of noise and vibration.
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Old 02-26-2023, 08:04 AM   #15
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Now to fix the jacked up duct!

After fixing the airflow issue I decided to pull the ceiling vents and check the ducts. They were pretty good....except....the kitchen duct on the drivers side. The pathetic excuse for employees at the factory crushed the duct, slapped some scrap plywood and foils tape haphazardly on it and sent it on down the production line. The QC on these things is terrible....but we still buy them! Now I get to figure out a creative solution to seal the duct with my only access being through the ceiling vent opening....fun, fun. Once I figure out a technical solution I will post that on here as well to hopefully help someone else out.
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Old 02-26-2023, 09:12 AM   #16
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So we recently purchased a "New" 2021 Alpine 3790FK from a guy that bought it to live in while he built a house. He never ended up using it and it sat on a pad, under a pole barn, hooked to power for a year. It was never used other than running the slides and "hanging out" for the day every month or so. Needless to say, we got a great deal. As with all rigs, we are fixing all the manufacturer mistakes but for the most part this rig seems to be well put together. The weather is warming up here in the panhandle of Florida and the AC volume and cooling just wasn't right. After reading through this thread I decided to yank the roof units and investigate....WOW!!!

Welcome to the forum and thanks for sharing your situation and repairs. Holt, FL? Are you at one of the RV parks; Eagle's Landing or River's Edge? We stay at Eagle's Landing a couple of times a year.
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Old 02-26-2023, 09:56 AM   #17
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Eagle's Landing

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Welcome to the forum and thanks for sharing your situation and repairs. Holt, FL? Are you at one of the RV parks; Eagle's Landing or River's Edge? We stay at Eagle's Landing a couple of times a year.
We sold our house in Gulf Breeze a year ago when our youngest graduated. We knew we wanted to move but since I am Civil Service it can take some time to find the right job so we just moved into our Trailer. Started off with our Mallard M25....it is great for trips to the lake but too small for full timing. We have been here at Eagle's Landing for almost a year but will move to Panama City in April for a new job at Tyndall AFB.
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Old 02-26-2023, 10:12 AM   #18
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Nice work and pics on the AC duct rework.. The 2020 - 2023 Alpines kind of fell short on the quality of work and QC inspections during assembly..

Your AC units will function much better now with twice the cold air and airflow.. Good luck with the collapsed duct repair...
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Old 02-26-2023, 12:51 PM   #19
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We sold our house in Gulf Breeze a year ago when our youngest graduated. We knew we wanted to move but since I am Civil Service it can take some time to find the right job so we just moved into our Trailer. Started off with our Mallard M25....it is great for trips to the lake but too small for full timing. We have been here at Eagle's Landing for almost a year but will move to Panama City in April for a new job at Tyndall AFB.

Congrats on the new job. Panama City will feel like a zoo after Holt. Was speaking to a couple across the road from us a few days ago from Panama City. They put an RV here (looks new) so they could get away from PC on weekends. Good luck with the job and location. We like it there for short bursts.
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