2020 Dometic A/C Problems - Page 3 - Montana Owners Club

Bruno B · 06-03-2020, 07:47 PM

I feel your pain as we have a 2013 Mountaineer which has had Dometic A/C issues since it was new. After numerous searches to resolve an intermittent problem I discovered that some wires on spade plugs that connected to the control box were not sufficiently crimped into the plugs. The wire would move around inside the crimp causing multiple make and breaks in the circuit. I resolved the issue by installing new spade plugs and making new crimps. On some of the crimp style wire nuts I also found debatable good connections. I have now soldered all of those splices and installed new wire nuts. Perhaps you want to really scrutinize all of the crimped connectors inside the unit.

RMcNeal · 06-10-2020, 04:16 AM

Well, I contacted Dometic 2 days ago and they recommended replacing the face plates. For a test, we removed both face plates and the A/C has been running properly since. No short cycling, shutting off and not back on, etc.
According to their rep, the foam inside the "buttons" gets compressed when pushed too hard and will cause all kinds of crazy results in the unit. They are shipping replacement face plates, but in the mean time, I'm running fine with them removed.
Hopefully, the new face plates will work, or I will try to find a thermostat without the capacitive touch "feature".
Thanks to everyone who chimed in.

bjacobs3791RD · 06-10-2020, 09:50 AM

I will second what RMcNeal stated. I have been back and forth on the phone with Keystone and two days ago after reviewing the videos, it was suggested that I pull the faceplates off, run them and see if the behavior changes.

The dealer and I both thought they were full of it and sending us down a rabbit hole, but after two days with no faceplate I have not had any problems. I'm not an A/C guy or electrician by any means, but somehow between the faceplate and foam behind the capacitive touch buttons, it caused the unit to demonstrate behavior that can't really be explained. Don't ask me how or why.

This is obviously a problem if Dometic and Keystone both suggested the same odd "fix". Now that it SEEMS to be working, we'll see what the real fix is. Until then, I'm running without the faceplate. Still have the LCD screen and three metal touch sensitive ends to control everything like normal.

I will post Keystone or Dometic's fix once I hear from them.

RMcNeal, let us know if you see any difference in the new faceplates when you receive them vs. your old ones.

mbjam359 · 06-10-2020, 12:12 PM

I meant to mention my 3931Fb was a Legacy package. My ac are controlled by a In Command System. I do not believe I am having any issues.

RMcNeal · 06-11-2020, 05:49 AM

Just a quick update...3+ days and all works fine with face plates removed. I noticed the new face plates have shipped, but I won't be home to get them and test for another 2 weeks. Until then, face plates are off and the A/C is working fine.
Thank you Sam (Mootana) and Brandon. You may have just saved my sanity, or at least what little is left of it.

duble0svn · 06-21-2020, 06:14 AM

I am having the same issue with my 2019 3791 with both A/C’s. When you say face plates is that the thermostat face plates or something else?

Thanks.

RMcNeal · 06-21-2020, 06:35 AM

duble0svn, yes it is the plastic thermostat face plates. Unfortunately, this doesn't seem to have solved the problem. According to Dometic, there is some sort of foam under the capacitive touch buttons that gets compressed when pushed too hard. They say you shouldn't "push" the button at all, but instead just tap it as if it were your smart phone. The original assumption was that the foam was compressed under the buttons and causing the sporadic issues.
After 2 weeks of running without these face plates, both units are now back to odd behavior. Sometimes they will shut off and not turn back on no matter how hot it gets. Other times, they will not shut off no matter how cold it gets. And other times, they do what I call a short cycle, where the unit runs for about 60 seconds, shuts off for 4 seconds, then runs another 60 seconds. This last one can be more or less than 60 seconds, but the off part of the cycle is always 4 seconds. Also, when doing this short cycling, the fan will sometimes be on high, other times on low. No rhyme or reason which one or when.
Brandon, bjacobs3791RD, has put up some you tube videos that shows this last behavior well. Unfortunately, my wife has had a death in the family so my troubleshooting has been put on hold while we prepare to travel home for family and funeral.

RMcNeal · 06-21-2020, 06:42 AM

Btw, with the face plates removed, you can still touch the metal blade where the buttons are located to control the thermostat. It won't hurt anything and won't shock you. I think this was asked before, so just wanted to clarify.

duble0svn · 06-21-2020, 06:50 AM

Thanks for the clarification. I have an appointment to bring my camper into the dealer on other stuff and I will see what they say about the a/c issues. I am thinking they will say we could not reproduce the issue. Lol.

RMcNeal · 06-21-2020, 06:51 AM

That's kinda been the consensus. I guess I understand that as it usually takes a while before the units start exhibiting the odd behavior. Maybe 12-24 hours or more.

**scottz** · 06-29-2020, 12:06 PM

I feel your frustration. I have been fighting similar AC issues for three years. My units (one or both), when the fan is on auto, will intermittently shut down and not start back up until I manually reset. If I keep the fans on high, no problems, just constant noise. I believe my units are freezing up.

It has been to three dealers and the Dometic guys at national looked at it. Unfortunately, the problem is intermittent and, of course, never occurs when they are looking at it. Thermostats & face plates replaced a couple of times; return ducts opened up; all the usual stuff.

I might have solved the problem with mine. Difficult to tell since we don't use AC that often and I think other factors such as humidity are in play.

I finally pulled lifted the units off the roof and found they had not been mounted over the holes in the roof properly. I suspect a portion of the cold air output was going directly into the return side and freezing the unit up. Keeping the fan on high keeps air moving and prevents the problem. Anyway, that is my theory and not sure if it helps with your problem.

Here is a link to a thread with more details and photos.

https://www.montanaowners.com/forums...ad.php?t=75245

GHallof · 07-01-2020, 06:40 AM

I am curious. It seems this issue has been ongoing for at least 4 years from the research that I have done. Many other sites like this one across other RV makes and models and their owners have the same complaints regarding these systems.

Dometic always seems to respond to customer/dealer complaints by creating a support incident for them and then walking through the same ole "TRY THIS", "THEN THIS", "THEN THAT" approach and after 4 years no end in sight it.

If there are any lawyers out there with experience in matters like this. Can you please help me understand why some sort of action in mass from a legal perspective would not be appropriate?

Gordo

bjacobs3791RD · 07-22-2020, 12:32 PM

UPDATE:

It's been a while since I've updated what the last month and a half looked like. The "faceplate off" solution worked for 4 days, thought we were in the clear. It returned back to its old behavior. Took it to the dealer, dropped it and said I didn't want the damn thing back until Dometic or Keystone had an ACTUAL fix. Long story short, after test this, bypass that, run it on this, switch it to that, they finally came up with a solution.....a THIRD replacement to the thermostats.

The dealer got the new thermostats in, installed them, ran it for a day and it seemed to be ok. I picked it up on June 30, had it plugged in at the house running for a few days then left for our beach spot on July 3. Last Tuesday, 2 weeks since I picked it up, I woke up to 77 degrees inside and set on 68. Back to same crap, different day. Ironically I received a call from Tom in Keystone's customer satisfaction dept. that same morning. We had a long discussion and I don't believe I left a single detail out. He called back Thursday and I was told to take it back to the dealer so they could go through diagnostics....WE'VE DONE THAT, multiple times, replaced everything there is to replace multiple times. They already have all the results from their diagnostic hoops they made Sherrod RV jump through. The conversation ended with him getting the product manager and Greg (individual that Sherrod's had been in contact with) involved and determine another route to go. No call back as of today.

I'm now $1,100, 2 months, into our summer spot and have only been able to enjoy it for less than 3 weeks.

Side note-- 2021 Montanas are shipping with Coleman Mach 15 units, Airxcel thermostats inside...

RMcNeal · 07-22-2020, 12:38 PM

Sorry Brandon. I really hoped bypassing the freeze sensor was the answer. I wonder if they would consider replacing our units with the Colemans?

bjacobs3791RD · 07-22-2020, 12:43 PM

Quote:

Originally Posted by RMcNeal

Sorry Brandon. I really hoped bypassing the freeze sensor was the answer. I wonder if they would consider replacing our units with the Colemans?

I'm pushing for that. I got the "Well, I'm not really sure what kind of units are going on the 2021 models" from Keystone, so I informed Tom of the change. We'll see how the next phone call goes.

How have yours been holding up?

mbjam359 · 07-22-2020, 12:48 PM

I thought we were good on our unit. Well sort of. Spent a week at the Frio River and both AC worked flawlessly. Ran them on high the entire time. Came home for a week then off to Crystal Beach the week after July 4. Rear unit worked for a day then would not blow cold air. Tried everything I could think of and dealer suggested. No luck. Had a Dometic certified guy look at it. It was froze up. He said Dometic had a vendor that didn't clean coils after they were manufactured and the units were built with trash in the systems. That trash has my orifice plugged up causing the freezing up. Unit being replaced under warranty tomorrow.

Mark - Texas
2016 F-350 DRW
2020 Montana 3931FB

R.S.O'Donnell · 07-22-2020, 01:03 PM

We stayed in our sons Radiance R-28QD trailer while going through the transition process from our "C" to our Montana 3121rl. It has the same Dometic AC units... The bedroom one works fine. The LR unit exhibits the same "berserk" behavior that has been described here. Neither has the covers on the thermostats.

Our class C Winnebago had a 15K Coleman. Always worked perfectly. We were beyond happy to see that our 3121rl came with the Coleman units. So far they have both been perfect.

**scottz** · 07-22-2020, 01:09 PM

Quote:

Originally Posted by RMcNeal

duble0svn, yes it is the plastic thermostat face plates. Unfortunately, this doesn't seem to have solved the problem. According to Dometic, there is some sort of foam under the capacitive touch buttons that gets compressed when pushed too hard. They say you shouldn't "push" the button at all, but instead just tap it as if it were your smart phone. The original assumption was that the foam was compressed under the buttons and causing the sporadic issues.
After 2 weeks of running without these face plates, both units are now back to odd behavior. Sometimes they will shut off and not turn back on no matter how hot it gets. Other times, they will not shut off no matter how cold it gets. And other times, they do what I call a short cycle, where the unit runs for about 60 seconds, shuts off for 4 seconds, then runs another 60 seconds. This last one can be more or less than 60 seconds, but the off part of the cycle is always 4 seconds. Also, when doing this short cycling, the fan will sometimes be on high, other times on low. No rhyme or reason which one or when.
Brandon, bjacobs3791RD, has put up some you tube videos that shows this last behavior well. Unfortunately, my wife has had a death in the family so my troubleshooting has been put on hold while we prepare to travel home for family and funeral.

When getting the "short cycles" is your fan in auto mode? When in auto mode, these units will momentarily stop and switch fan speeds high>low as the thermostat set point is approached. Then repeat going from low>high as temp rises. Just a thought.

The behavior of these units (working ok for days/weeks, then shutting down, repeat) is very frustrating; for us and the techs that have to work on them. I've pretty much given up and run my fans on high all the time. My units have never not cooled; if they run, they work great.

cghsatx · 07-22-2020, 02:18 PM

Quote:

Originally Posted by scottz

When getting the "short cycles" is your fan in auto mode? When in auto mode, these units will momentarily stop and switch fan speeds high>low as the thermostat set point is approached. Then repeat going from low>high as temp rises. Just a thought.

The behavior of these units (working ok for days/weeks, then shutting down, repeat) is very frustrating; for us and the techs that have to work on them. I've pretty much given up and run my fans on high all the time. My units have never not cooled; if they run, they work great.

I got the run around for 2 years and now have no warranty. Its been checked by dealer 2 or 3 times, Keystone, Dometic, independent RV repair (said units were full of dirt and cleaned them) and no one finds anything wrong that solves the problem. Was at Lake Travis over the weekend. Was cooling most of the day. Then the bedroom AC stopped cooling (was 94 in there). Turned it off, waited about 5 minutes and turned back on. Then it cooled down the room. I turn the bedroom unit off at night, as it has to be on high to cool but also vibrates the flimsy bathroom curved wall and door. The front LR AC works better but if you sit on the couch , you can feel a vibration from it. Thermostats have been replaced, reset, filters cleaned, tried on auto, high and low and nothing seems to keep these in a cooling mode throughout an entire day. In addition to other items, I can hardly wait until the note gets paid down enough to unload it

bjacobs3791RD · 07-23-2020, 08:16 AM

Quote:

Originally Posted by scottz

When getting the "short cycles" is your fan in auto mode? When in auto mode, these units will momentarily stop and switch fan speeds high>low as the thermostat set point is approached. Then repeat going from low>high as temp rises. Just a thought.

The behaviour of these units (working ok for days/weeks, then shutting down, repeat) is very frustrating; for us and the techs that have to work on them. I've pretty much given up and run my fans on high all the time. My units have never not cooled; if they run, they work great.

Scottz,

The switching in auto mode from high fan to low fan happens as it approaches 5 degrees away from the set point (I think that's a little early, but that's for another day).

Last week when it shut down on me it was set on 68/High Fan. When I woke up, it was 77 degrees inside, fan running on high, compressor off. As always, went through the modes, off, back to cool and the compressor kicked right on. The fan actually never even shut down.

It seems it's frustrating for everyone except Dometic and Keystone. I'm tired of it and I know the guys at Sherrod RV are tired of getting the runaround. No telling how many hours they've wasted working on this, waiting on hold (1hr 45min when I was up there one afternoon), etc. Time they could've spent fixing other rigs, it's not like mine was the only thing they had going on.

Brandon

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