Dometic Thermostat on 2020 single AC unit

[Justinfinity]

2020 Globetrotter, single AC unit, Dometic thermostat control mounted in front twin bedroom, on the "port" / driver side cabinet below the television.

Problem: "INSIDE TEMP" reading on the Dometic control "wanders". It's not that it is simply off by a fixed difference from actual temperature (read by another thermometer). That would be easy to deal with because you could just set a comfortable "make believe" temperature and be done.

No, the difference between the "INSIDE TEMP" reading on the Dometic control and a separate thermometer can differ by as much as 20F *AND* the difference will change, sometimes rapidly, from only 1F (which would be fine) to 20F.

I have actually seen the "INSIDE TEMP" reading *increase* by several degrees while the AC is on and the trailer is actually getting cooler.

Put the whole thing on AUTO and the trailer goes on a roller coaster ride from freezer to sauna and back. Oh, and that rapid temperature change makes every surface (walls, mirrors, etc) wet.

Already had the control unit replaced. No change.

Already had the trailer into the dealer for service. No change. I suspect the dealer "technician" turned on the AC, left, came back, and said "it's cooler, it's working" and never addressed the subtlety of the real problem.

Any thoughts?

[AirstreamInc]

Originally Posted by Justinfinity

2020 Globetrotter, single AC unit, Dometic thermostat control mounted in front twin bedroom, on the "port" / driver side cabinet below the television.

Problem: "INSIDE TEMP" reading on the Dometic control "wanders". It's not that it is simply off by a fixed difference from actual temperature (read by another thermometer). That would be easy to deal with because you could just set a comfortable "make believe" temperature and be done.

No, the difference between the "INSIDE TEMP" reading on the Dometic control and a separate thermometer can differ by as much as 20F *AND* the difference will change, sometimes rapidly, from only 1F (which would be fine) to 20F.

I have actually seen the "INSIDE TEMP" reading *increase* by several degrees while the AC is on and the trailer is actually getting cooler.

Put the whole thing on AUTO and the trailer goes on a roller coaster ride from freezer to sauna and back. Oh, and that rapid temperature change makes every surface (walls, mirrors, etc) wet.

Already had the control unit replaced. No change.

Already had the trailer into the dealer for service. No change. I suspect the dealer "technician" turned on the AC, left, came back, and said "it's cooler, it's working" and never addressed the subtlety of the real problem.

Any thoughts?

Hi Justinfinity,*

We're very sorry to learn about the issue you are having. Please send us a direct message with your contact information, email and the last 6 digits of your VIN so we can learn more and share it with our Customer Service and Technical Support team. We look forward to helping you get this resolved.


Thank you.

[Spec7op]

Originally Posted by AirstreamInc

Hi Justinfinity,*

We're very sorry to learn about the issue you are having. Please send us a direct message with your contact information, email and the last 6 digits of your VIN so we can learn more and share it with our Customer Service and Technical Support team. We look forward to helping you get this resolved.


Thank you.

2021 Flying Cloud FBQ

I’m having the same issue with my Flying Cloud. The thermostat reads about 10 deg higher most of the time, although periodically it will go off into the ozone like you describe. But be thankful. I’ve had my new trailer on its third voyage and had about everything in it go off the deep end. Like the tankless water heater can’t decide if it wants to be scorching hot or freezing cold with a slight touch of the valve. Or the exhaust fan over the stove quits working when the stove gets too hot ( really isn’t that what it’s for?). Or the fridge Willy Nilly stops working if the trailer isn’t totally level ( lost 2 loads of food to date). Or the fridge makes a racket when we’re ready to go to bed because it’s too hot outside (turns out to be the cooling fan needs replacing). We are finding rivet heads on the floor ( is this normal??). Or the tires are not all the same load range (3 are 80psi load range E, and one is 65psi load range D- Airstream has made this good and sent us the correct tire!).

Would I buy a different trailer, probably not- I’m a sucker for Icons and at this stage in life not sweating pennies. The good stuff- coolest spaceship ever made, never slept better than on the queen bed, easy tow, holds its value, and makes the wife happy. Also being an engineer I can usually come up with a work around for the problems. Happy camping!

[WoodGrain]

Remove the return air grills and see if a remote sensor was installed in your system. If you have one, unplug it. We had a similar problem with our 2018 27FB Globetrotter. Our trailer has 1 A/C unit.

A remote temperature sensor was installed in our trailer. This was an error as we have only one A/C unit. There was no room cut-out for the sensor and cap and so we had no idea it was there. This sensor was picking up the temperature between the wall and fridge and using this value to control the system.

A mechanic at Bill Thomas RV discovered the remote sensor and simply unplugged it. The sensor connection is in the ceiling above the return air grills.

This remote sensor is a white cable with a plug end. Google Dometic 3106486008 remote sensor kit for a picture of the cable end.

[amxpress]

We have the standard Dometic thermostat. I was speaking with another AS owner who installed a digital thermostat and really likes it. He said it was much more accurate and easier to operate. It’s on my Christmas list. This the one he installed: Honeywell TH1100DV1000/U Pro 1000 Vertical Non-Programmable Thermostat

[John & Roberta]

Roberta and I find rivets regularly. Sometimes there’s a bit of a stem on them and sometimes it’s just the flat tip. So far—8,000 miles in the year we’ve had our trailer—we’ve not found a rivet hole to go with the loose ends. Finding a loose rivet and NOT finding the hole it came from are both worrisome.

John designed and built custom homes for 35 years, frequently doing electrical, plumbing and heating himself, so he’s not afraid to dive in when a problem arises. But, in this first year with a trailer we bought just a year old, there’s always a serious problem in front of us. The refer not working on LPG, the hyper-complicated thermostat . . . and now our furnace no workee.

A small problem as compared to the refer and furnace, when John replaced one of our skylight shades—first owners were short and probably used a broom handle to extend and retreat the shade—he discovered evidence of sloppy installation and/or poor quality control. (Heads up, AirstreamInc.) A “quick install” would have the installer fit the shade up tight and all the way left or all the way right, leaving a 3/8-inch+ gap on the not-tight side. It’s trickier CENTERING the shade, and might even require assistance, heaven forbid. Result: a sloppy look and sloppy operation.

As we’ve said before, this coming up to speed on Airstream is not for sissies.

Our Flying Cloud 30RB has two air conditioners and is designed with two zones, Zone 1 aft where the thermostat is and Zone 2 forward where the refrigerator is. The Zone 2 sensor is attached to the refrigerator wall and reads a temperature not characteristic of its zone and certainly not characteristic of the trailer’s overall interior. The thermostat’s User’s Manual is page after page of user unfriendly discourse. At home, it’s flip the thermostat cover up to make adjustments, and there find all the instructions necessary to manage a heat-pump/AC unit covering a two-story residence: a few sentences addressing time and date and a few more covering temp ranges. Works without a hitch. Come on Dometic, let’s get real.

[BayouBiker]

As mentioned, if an optional remote sensor was installed accidentally, that could cause an issue. Otherwise the sensor is integrated with the thermostatic controller and may be malfunctioning. Check for a remote sensor and disconnect as suggested. Otherwise have Airstream send you a new CCC2 controller.

The Stove vent fan trips its motor thermal protection especially with more than two burners on at the same time because the fans are a bit too close to the range top. there is a thread or two on how to correct this issue. I don't remember exactly what that fix was.

Can't suggest anything about the refrigerator issues.

[Justinfinity]

Well, this thread went off the rails quickly.

I started the thread as "Dometic Thermostat on 2020 single AC Unit".

Can we keep it focused?

[Justinfinity]

what?

[BayouBiker]

Hmm, Seems like you were given some pretty useful things to look at. Did you check for a misplaced and not needed remote sensor? You didn't say. In the mean time others mentioned they had the same issue and some others... Would be a shame to ignore their other issues, don't you think?

You mentioned the CCC2 has been replaced and made no difference. If you were to come back and report there is no remote sensor attached, I would have suggested the Roof unit Controller board may have an issue. I would have suggested the dip switches be cycled and reset correctly, all power removed (110 and 12 V), the CCC2 be reinitialized and try again. If that doesn't work I would fault the rooftop controller board, but it could also be a poor connection causing rooftop unit control voltage to vary. You might check for sensor wires laying in a pool of water up on the roof unit, and you might disconnect the furnace leads temporarily.

[targetdesign]

I am having what sounds like the same issue with my 2020 FC 25RBT with one AC unit. It is my understanding that when you have only one AC unit, the temp sensor is in the thermostat itself. However, my Airstream (and yours) is available with 2 AC units, and in that case the small temp sensor near the main area TV controls the second zone temp. This sensor is right by my fridge and next to a wall that can get very hot if you're in the sun. Thermostat said it was really hot in the trailer. I held a cold gel pack over the second zone sensor, and GUESS WHAT, in about 90 seconds the thermostat reading dropped 20 degrees and the A/C unit shut off (otherwise it just runs constantly, trying to cool down the very hottest point in the trailer while everything else feels like an ice box. I checked the back of the thermostat, and the RJ11 wire is clearly labeled 2nd AC.

I am now trying to decipher if there is a "First AC" RJ11 wire that was not hooked up properly at the factory or ??? It has been in for warranty service on this issue TWICE and they said there's nothing wrong because clearly it blows cold.

At the thermostat, it shows it's operating Zone 1 and there are no other zones to select. Haven't tried finding and unplugging the AC sensor wire, but that might be my next step. Other ideas are welcome.

[Justinfinity]

After a lot of persistence, I finally got the dealer to focus on the problem. They found that a sensor was incorrectly wired in the plenum, which is exactly consistent with the observed behavior. The plenum would heat up and or cool down depending on the settings and the actual ambient temperature of the coach would never reach the desired target because there was effectively no active sensor in the living area of the coach itself. In fact, because the "active" sensor was located in the plenum near the heat exchanger coil of the AC unit, the whole system was behaving in reverse: when I set the unit to cool, the coil would heat up and the sensor would "believe" that the temperature had actually increased in the coach when in fact it was a meat locker. Ands vice versa. It was maddening.

Once they disconnected the incorrect sensor located in the plenum this allowed the sensor in the CCC2 control unit (located in the bedroom area of the coach) to do its job. If yours is anything like mine, the plenum is a rats nest of wires that may or may not be connected due to the fact that there are optional 2nd AC units on some models and not on others.