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Old 05-08-2017, 04:26 PM   #1
usaf_retired
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3791RD A/C Issue

We have a 2017 3791RD. Just started having a issue with one of the Dometic thermostats. When it's running, the A/C works fine. But when it reaches set temperature and stops. It will not start back up again, when temp rises. I have to shut it off for about 30 seconds, then turn it back to A/C auto is where I have been setting it on. Then works ok. Thinking it might be a bad thermostat. Any suggestions please. Also though about swapping it out with the one in the bedroom to see if trouble follows.
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Old 05-14-2017, 08:20 PM   #2
Golfmedik
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Originally Posted by usaf_retired View Post
We have a 2017 3791RD. Just started having a issue with one of the Dometic thermostats. When it's running, the A/C works fine. But when it reaches set temperature and stops. It will not start back up again, when temp rises. I have to shut it off for about 30 seconds, then turn it back to A/C auto is where I have been setting it on. Then works ok. Thinking it might be a bad thermostat. Any suggestions please. Also though about swapping it out with the one in the bedroom to see if trouble follows.
Ours is doing the same thing. There is a TSB out from Dometic saying not to run the Ac units with the T-stat in AU or LO mode in a humid environment as they will freeze up when they start to shut down. Ours front AC unit does it every time in the LO position as my wife doesn't like it on HI. BTW, according to Dometic, these new thermostats do not go bad
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Old 05-15-2017, 02:24 PM   #3
MAwolcott
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I wonder if that is what's wrong with mine. My main A/C unit isn't putting out cold air. I have an appointment to take it back to the Outlet I bought it at on the 25th so they can repair it. They ordered a new A/C just in case...Camping World wouldn't have done that!!
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Old 05-16-2017, 07:42 PM   #4
kozzy
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Same Thing

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Originally Posted by usaf_retired View Post
We have a 2017 3791RD. Just started having a issue with one of the Dometic thermostats. When it's running, the A/C works fine. But when it reaches set temperature and stops. It will not start back up again, when temp rises. I have to shut it off for about 30 seconds, then turn it back to A/C auto is where I have been setting it on. Then works ok. Thinking it might be a bad thermostat. Any suggestions please. Also though about swapping it out with the one in the bedroom to see if trouble follows.
I was just about to start a new thread, looking for answers myself. Mine does the same thing, has from day one. My main AC works fine and as expected, my upstairs AC will turn on, get the room to temp, and then shut down. When it warms back up, it will not kick on. I have had it in twice to CW for this problem, the first time they replaced the thermostat and said it was good... NOPE, same issue. This second time, they replaced the AC control board, said it worked. NOPE, does ths same thing. Ill be calling them and Dometic tomorrow....please share any results you get, im so frustrated with this.
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Old 05-17-2017, 07:08 AM   #5
navybanker
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Does your unit leak water from the outlets? Not the returns. Mine is cooling but drips water. Fan always on high.
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Old 05-18-2017, 10:06 AM   #6
JABURKHOLDER
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I feel bad for saying this but I have no problems with mine. I have a 2016 3791RD. I set the thermostat at 70 for both zone 1 and zone 2. The fan is set to auto. When the "set" temp is reached in which ever zone, the appropriate unit shuts off. When the temp goes up in which ever zone, the appropriate unit turns on. Just as advertised.
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Old 05-20-2017, 09:33 PM   #7
Snoopy
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Just brought our 352 rl HC to selling dealer for similar issues. Our single zone ac living room unite tends to cool our rig more than the thermostat calls for. set to 78 and it does not shut off till round 71 in the rig. replaced thermostat once and it still seems to do the same. went up to cold country for a long weekend and had similar problems with the furnace. rig got warm on furnace setting of 71, lowered temp 69 and heard furnace shut down. furnace did not came back on for over two hours. coach dropped to 53 degrees inside before furnace refired. Worked fine rest of weekend.
Any Ideas?
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Old 05-23-2017, 02:59 PM   #8
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problem with AC

My dealership is now fighting to get keystone to add a third AC unit to keep up with the demand because the size of the 2017 Montana. The unit freezes and kicks off and does not restart as temperature increases. The unit is wired for a third ac. Keystone is trying to get the the dealership to move the thermostat. That would require a total rewire. Since the unit is wired for a third unit. The easiest solution is to add the new unit. I would contact keystone and fight for this solution. If enough owners are experiencing this same problem they will have no choice but to fix the problem correctly.
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Old 05-24-2017, 08:45 AM   #9
DQDick
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I asked the dealer selling us our new one about the third AC option and they feel that you'll still only be able to run two at a time due to electrical constraints.
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Old 05-25-2017, 06:56 AM   #10
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I've learned something pretty interesting the last couple of days. Montana put two 15k AC units on my unit, the 3790RD. That means that it will take 50A to run them both. I found out that FR has put on the traditional 15k and 13.5 units on their new 3950TZ, along with a third unit. They do have the new Power Management system on them to run all three units, but the interesting part is that they can run only two(one rear and the 13.5 unit in front) due to the fact that the new units put out by Dometic don't draw the amps the older ones did, without the PMS engaged. They claim they can now run the two on a single 30A pole. Interesting!
Here is the link to the FR factory rep talking about it. Near the end of the video.
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Old 05-26-2017, 03:51 PM   #11
jameswbarton
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Wow if you need three 15,000 btu units which is almost 4 tons of AC your coach of say 400 sq ft must be lacking in insulation or you have a few windows open or live in death valley. Hope I do not have to pay the electric bill on that setup.
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Old 05-26-2017, 04:15 PM   #12
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Wow if you need three 15,000 btu units which is almost 4 tons of AC your coach of say 400 sq ft must be lacking in insulation or you have a few windows open or live in death valley. Hope I do not have to pay the electric bill on that setup.
OR you have the newer styled AC units that LOTS are complaining about.
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Old 05-26-2017, 04:20 PM   #13
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That's why I'm asking. Spend the summer in Kansas with 100 degree temps and 90% humidity. we're getting a new rig with the new quiet AC units and loosing the slide toppers and double pane windows so I'm investigating my options.
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Old 05-26-2017, 05:00 PM   #14
jameswbarton
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Golfmedic, Newer Dometic Units than my 2016's Blizzard NXT 15,000 btu and the Penguin II low profile 13,500 on mine? I did have to have the blizzard NXT removed and properly installed.
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Old 05-26-2017, 06:25 PM   #15
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Golfmedic, Newer Dometic Units than my 2016's Blizzard NXT 15,000 btu and the Penguin II low profile 13,500 on mine? I did have to have the blizzard NXT removed and properly installed.
I'm talking about the entire line of Dometic ACs that do not have the quick cool feature and only ducting. BTW, my rig has two 15s on it. Not a low profile on the front. The new roof lines allowed them to put 15s on both ends.
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Old 05-26-2017, 06:43 PM   #16
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My Blizzard NXT 15K must be new it is only ducted with two ceiling returns. The Penguin II is on the same ducting but has the dump grate and the return air is in the grate. My Montana is close to 14 feet tall as it barely fits into the warranty dealers 14 foot door. I am guessing it is 13'6" or more and its high point is the low profile penguin II mounted in the front.
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Old 05-29-2017, 08:05 AM   #17
phillyg
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Had the same problem. I bought and replaced the inexpensive thermostat because we were travelling and couldn't get to the dealer. Didn't fix the problem. Finally got to the dealer and Keystone authorized replacement of the board in the a AC unit. Basically fixed the problem but it still occurs on occasion..
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Old 05-31-2017, 10:00 AM   #18
4blys
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We have a 2017 3791 RD. We took it in for service on the AC.The bedroom AC was short cycling and they could not replicate the issue. However, they did see where the other AC would not turn back on so they replaced the thermostat. We had no issues with that one this past weekend. Will be taking it back to fix the bedroom AC.
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Old 05-31-2017, 03:55 PM   #19
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Quote:
Originally Posted by DQDick View Post
That's why I'm asking. Spend the summer in Kansas with 100 degree temps and 90% humidity. we're getting a new rig with the new quiet AC units and loosing the slide toppers and double pane windows so I'm investigating my options.
Whoa Dick! Glad to see you are moving up but I'm betting you should have stayed with the toppers and DP windows.
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Old 06-11-2017, 05:52 AM   #20
kozzy
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Originally Posted by Golfmedik View Post
Ours is doing the same thing. There is a TSB out from Dometic saying not to run the Ac units with the T-stat in AU or LO mode in a humid environment as they will freeze up when they start to shut down. Ours front AC unit does it every time in the LO position as my wife doesn't like it on HI. BTW, according to Dometic, these new thermostats do not go bad

When you leave the fan mode in HI, does this prevent the unit from freezing up and it work normally?
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