Dometic AC stops cycling

I hate to bring up a year old post, but I'm having the exact same problem. I changed the thermostat with no results. Did you ever find out what the problem was with yours.

 

I had the same problem - exact same symptoms. The sequence of events was - the AC runs until the coil freezes up. The freeze protection sensor cuts the unit off and won't allow it to cycle back on. It won't reset until the thermostat is manually cycled off then on again and the process repeats. If the ambient temp is low enough for the AC to keep up with the set point, the system works fine. But when the outside temp increases and the AC can't keep up, the coil freezes and the problem starts. This sequence doesn't happen when the fan is on (continuous fan) because the coil doesn't freeze.

One earlier poster commented that it may be low on freon. Low freon will cause a unit to freeze up, but so will low air flow. In my case the problem was an air dam between the input chamber and the output side had fallen out of place and allowed the output air to recirculate back to the input chamber. A couple of sheet metal screws and some aluminum tape fixed the problem. I think this is a common problem with Dometic units.

This is a pretty easy fix (or just to check) if you are up for it. You'll have to pull off the faceplate from the AC unit - 4-5 screws , the filter and the knobs. Check the position of the air dam to make sure there are no leaks between the input chamber and output side. The air dam should not rattle or move when you push on it.

There are other reasons the unit will freeze up, but that's a pretty easy check. If it's freezing because of low freon, it's difficult because these are basically "throw away" units. I don't think most of them even have access valves.

Good luck.

 

Did you ever figure out what was wrong? My husband uses our camper for work, and he’s having the exact same problem you are, and ours is only 6mths old. It’s under warranty, but unfortunately Camping world can’t even help him for almost a month

 

With all due respect, you've responded to a thread that is a year old. The participants may not be active on the forum at this time. You would be better served by creating a new thread about your particular problem.

Joel ((AKA docj)

 

I have a 2018 EVo dometic air conditioner with the same issue..called support ect..no fix. After stumbling upon a youtube video of a guy with same issue and found a fix.
If you remove the air filter cover for intake you will see a white foam insulation towards the vent side of aircondtioner. It is held in place with double side sticky tape (kinda cheesy). I guess with the air pressure when you switch from down vent to ducted vents it causes it to come loose and sends cold air back into intake. I used gorilla tape to keep in place after making sure it is seated properly..sure hope this helps

 

Just had a brand new dometic unit installed
It's a 15000 btu
The unit will seem to cycle fine and then for no apparent reason will not turn on as the temp in the RV climbs out of control
This has occured many times and can vary as to time of day and outside temp demand
The company we bought the unit from has honored the 30 day buyers warranty and had a Control Box and Thermostat sent as well as a freeze sensor
Those parts were replaced yesterday and today at 4pm the temp in the RV ran away to 82 degrees and the dometic never cycled even though the system by all appearances looked fine and was cycling fine all day.
The way to get it to start again is to goto the thermostat and goto off mode wait a minute or so and then turn it back on again.
We have reset the thermostat and that has not worked to fix the issue.
I am very frustrated at this point and saw these posts here on this site.
The problem with a digital thermostat is it communicates with the control unit in a serial fashion.
Codes are sent to issue commands that function the unit.
This handcuffs the user from troubleshooting unless he has a way of seeing that the start cycle or cooling on command has been issued and the unit is ignoring it or it has been issued and the unit doesn't process it.
Both the control box and thermostat were replaced as I mentioned earlier so I just don't understand?
The outside air temps here have been milder but the demand for AC still exist.
So a freeze issue shouldn't be the case.
In this thread there are a few that have had the same types of things happen and one of them mentions a duct type fix on the inside of the unit which I don't quite understand as the unit would have to be on and functioning to connect the room air to the conditioned air.
Anyway does anyone have the fix for this as I am very FRUSTRATED!
Thanks and Happy Camping

 

I sighned up just to chime in on this issue. I never saw the video that cav scout mentiond. However, I did take my unit faceplate or vent plate apart to have a look. I was having this exact same issue on a new 2020 unit. Sabre 36bhq to be exact. I took it apart because it was shutting off and I knew it was freezing up and I was quite certain it wasnt a compressor or refrigerant issue as its not even a year old. I was strongly leaning towards the thermostat. However I noticed the unit worked fine as long as I had the vent opened so that it was blowing out of the unit rather than through the AC ducting throughout the camper. I saw exactly what cavscout mentioned that he saw in the video. the cheap white foam that was moderatly sticky cant remain stuck with the air pressure, tempuerature and moisture from condensation. This allowes the super cooled air to imediatly return to the unit where is cools super cooled air again and again until it freezes up. This is indeed the culprit. mdcamping is wrong. His logic is sound except that there are numerous complaints of this all on units less than a few years old in most cases. The reason can not be they all have the textbook low freon, bad thermostat situation. If you have found this thread while seeking an answer to your problem as we have been discussing. You must first look inside your unit to insure you dont have the same situation as I and cavscout have realized. keep it simple, dont automatically condemn your unit as having crapped out.

 

Yep, I've had the same problem - same symptoms. My experience was shared in post #22 in this thread. The problem is caused by air leaks between the input chamber and output side. This is the same thing Cavscout found in his AC. His fix is repeated here:

I also taped the white foam back to provide a complete seal, but in my case the actual metal air dam was pulled away. Either way, you just have to stop air that should be going out to the ducts from circulating back to the return side, "short circuiting" the normal path.

 

I have been dealing with the same issue. We are in Texas and when ever it gets above 85 degrees outside at some point intermittently the unit will not come back on. I assumed the unit and a safety cutoff after the unit has stayed on for a duration of time. They may have designed it this way to prevent over running the system. I have experimented rotating the vent and raising the temp. It seems whenever the temp is set too or the vent facing away from the tstat during a hot day it times out. I have not confirmed with dometic or the manual on this.

 

We have the same issue with our dometic ac as described. We bought our jayco jayflight brand new January 2, 2021 and now it’s mid March 2021, the start of air conditioning season in south west Georgia, and it keeps knocking off. When we get back home tomorrow I’m going to check that air dam and see if it’s fallen out of place. No issues with tstat working with the furnace last month. Only gives trouble with ac.

 

We have had these same issue of AC not cycling or Turning back on. We have been camping out in General RV parking lot for three and a half weeks now. They have worked on and replaced about everything you could possibly replace except the actual ac unit. They have been very accommodating here. However, even though they found many issue, nothing has fixed the problem. We are checking out what you have mentioned here and praying this is the Fix as we are out of options and must head home next week.
If this works, I will be back to let you know.

 

Ok. We have been in General RV Parking lot for an entire month. Many problems were found BUT, thank you so much for telling us about the gaps in the input/output. The next day I told the guy to get up there and check it out. Huge gaps. He taped them all up tight. The the next thing he did which we also believe was a huge fix along with that was he moved the freeze sensors from down low, to up high. So the ac was freezing and since the sensor was so low it would not keep running nor would it turn back on and we believe the reason it almost always quit working at night was because it took a long time with temperature drops and no sun for it to thaw. Now it is working like a champ!! So thankful we found this thread!!!!

 

We just bought a MHC 295RL and we are seeing this issue with the rear AC unit. It will run cool down to set point, cycle off and will not come back on until you cycle the 120VAC to the unit. kind of frustrating. I will be checking the return / supply seperator when we get to the campgroudn this weekend. Hopefully that is all it is.

Thanks for the insight!!

Bo

 

My domestic unit on my 2019 Jayco had these symptoms last season. What I found during the off season was a massive gap above the divider on the off-door side about 1/3 the length of the divider and about 3/4” tall. I filled this with AC foam and taped over it. With one trip in the books this season, AC worked flawlessly.