Dometic HVAC Control Problems

I honestly have no idea what is going on with this Dometic fresh jet air conditioner. There must be some electrical interference from somewhere diturbing the control box or thermostat. If I ever get this figured out I will do a followup video.
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[@echo242372]

Heart me out. I had the same if not identical problem and I have the same thermostat and AC Unit. My AC would work fine, but when it seemingly reached temperature, it would shut off and not come back on when the temperature rose. I would have to go to the thermostat and cycle the AC OFF and cycle the AC back ON to get the AC to come back on and the cycle would repeat. On a rare occasion I would hear what sounded like rocks kicking around in the blower motor. It was ICE.. Cooled AIR was leaking back into the supply side and freezing. I pulled the panel off and resealed around the supply side with aluminum foil tape. That fixed the ice problem Maybe coincidentally, but ever since I sealed the supply side, my other issue with my AC not coming back on after it seemingly reached temperature completely disappeared. My AC now turns off when it reaches temperature and comes back on after the temperature rises a few degrees. I hypothesize the thermostat was not turning the AC off when it reached temperature but instead it was turning off in response to an alarm state. Cycling my AC OFF and back ON at the thermostat would reset the alarm and it would work again till the alarm occurred again. In my case, perhaps the AC was turning itself off because the freeze sensor was doing its job when ICE was forming. Maybe something similar is going on here.

[@hillbillyrv]

Thanks for the input. I installed this AC a few months ago. I sealed it real good. We have another issue.

[@darylhawkins4658]

@@hillbillyrv You’re doing great. I’m sure you already know this. if the humidity is high the evaporator can freeze up. Try setting the blower fan to either Hi or Lo, not Auto, so the blower fan runs all the time. This keeps air moving across the evaporator and circulating inside the RV. The compressor will cycle on and off as it needs too. The customer will hear an audible thump in the ceiling when it does.

[@hillbillyrv]

Yes sir, got it. @@darylhawkins4658

[@darylhawkins4658]

@@hillbillyrv did you take down the 220vac mis wired shore power video? It’s one of my favorites.

[@hillbillyrv]

I have not taken down any videos. @@darylhawkins4658

[@patrickstiltner1207]

Great video as always Kenny! Can't wait to hear the follow-up.

[@hillbillyrv]

More to come.

[@daviscrt]

I never heard of a ac ripple until watching you and Daren talk about it it a few of your older videos. Thanks Don

[@hillbillyrv]

It used to more prevalent..

[@joesmith3899]

Always good stuff. I dealt with same issue on a Coleman-Mach recently. Initially swapped the thermostat but ended up swapping the control board. Jury is out if it fixed the issue... Interesting information regarding the AC Ripple interfering with the operation... If it happens again - I think I would ask the customer to make a list of everything else that was running on both the AC and DC side of the coach... may lead to the issue.

[@hillbillyrv]

Thanks. Good idea.

[@redcauthen771]

Awaiting the outcome 😊

[@hillbillyrv]

Me too.

[@supertuner5904]

Any update. I'm having the exact same thing. 2018 dometic unit.

[@randydouglas5153]

I want to say thank you, I have an older unit, 06, with a domestic AC, went out, I changed hard start capacitor, run capacitor, I changed the analog thermostat, and the relay board, ( watched your ved, on changing analog to digital, got scared) still nothing!!! I don't know what else to do, so right now I'm hard wired from 120v to high fan and compressor

[@henrymorgan3982]

When you are chasing intermittent bugs having parts to diagnose is smarter than smart. People who comment about using the part then "charging" for a part do not understand the time and effort you put into these jobs. Just the travel time alone cost time and fuel. The other part of the equasion is how much time is "saved" to having spare parts on hand. Hope you find the bug!

[@hillbillyrv]

Thank you Henry.

[@KevinCoop1]

Just my personal opinion. You’ll be back. And my professional opinion. You’ll be back. I’m thinking you might just have a loose hot or ground somewhere feeding the control box or from the box to the thermostat. Electronic components do very strange things when somewhere a not so good connection to ground exists. But, I’m sure you will figure out what’s wrong, eventually.

[@hillbillyrv]

I have already been back. I am still trying to figure it out.

[@KevinCoop1]

@@hillbillyrv I found something for you to try. Turn the fan to on, not auto. See if it cycles. Some report it runs fine this way. Also, it is suggested that there is a way to re-initiate the Tstat and reset the Tstat and control box. There are many many posts about Dometic AC doing this. It seems they have poor quality control during manufacture of the Tstat. Best wishes

[@Shrav2112]

Love your step by step approach. Any update? Our new-to-us 2015 Open Range is doing exactly the same thing. If I turn the fan to high or low-> then switch on cool and then fan back to auto, works fine until it hit target but won't start on its own again. If I leave the fan setting on high and run the a/c, I can hear it cycle on/off at temperature but obviously the fan keeps running. When I ran the furnace a few weeks back it cycled normally so I know that part is working and responding as designed. Hope you find the issue because I'll be following step by step too!

[@hillbillyrv]

This video is from last summer. There was no part 2.

[@Zihuatanejo...]

Where did you get the dvm gnd probe at the 21:28 mark? Looks heavy duty. Also, if the freeze sensor is detecting ice, wouldn't that cause the AC not to come back on?

[@hillbillyrv]

I have those meter Leeds in my Amazon store and yes the freeze sensor can do that.

[@douglasmayherjr.5733]

Interesting Diagnosis, Kenny. It would be interesting to see the AC and DC wave form or straight wave on a scope meter. Be nice to know if it fixed it. Thanks for the videos.

[@hillbillyrv]

I don’t have a scope.

[@ScottDLR]

Yes and a multimeter isn't the best tool for measuring ripple.

[@trehonsey4958]

I was wondering if there was any update on weather or not there was any update. Did the converter swap resolve the issue?

[@hillbillyrv]

Believe it or not.....still working on it.

[@jasonisom6652]

Has the issue been discovered yet? Mine does basically the same thing, except when I wake up in the middle of the night mad. And irritated because I'm sweating, I can cycle the thermostat. Turn it off, wait for the light to turn off and then turn it back on. And it will work perfectly as expected for the rest of the trip.

[@hillbillyrv]

I never got to finish the job. I really think it was electrical interference, just not sure where the interference was coming from.

[@justsendit8462]

So, did that fix it

[@kylethompson2017]

I'm curious on a couple things. What happens when it's set to "HI Cool" instead of "Auto"?? Also, is the freeze sensor good and plugged into the proper location? I'm assuming you've looked at all that but since you didn't mention it, I thought I'd throw it out there.

[@hillbillyrv]

As far as I know the fan speed has only been run in auto and yes, the freeze sensor is good and correctly installed.

[@TravelingonAdventures]

Have a feeling that isn't going to fix the issue. Curious to see what the outcome is.

[@hillbillyrv]

I hope I can figure it out.

[@ScottDLR]

Could it be the industrial strength margarita machine he runs in the evening? If so, let us know what time.

[@hillbillyrv]

Hmmmm?

[@ScottDLR]

@hillbillyrv Sorry, big electric motors working hard tend to make electrical noise that can interfere with stuff 😬

[@user-sz2gu2il2w]

No warranty on the converter? You stated you will charge him for the converter.

[@hillbillyrv]

This was last year so I don’t remember everything I did or said in the video, but electrical components have pretty short warranty periods

[@billking1558]

So if you had found ac ripple what would you have done to fix it?

[@hillbillyrv]

Replaced the converter. There are filters in them to filter out the AC current in the DC.

[@billking1558]

If I ever used vice grips on what looks like a craftsman screw driver like you were using, I would get a hand to the back of my head from my father or uncles. I was also told those screwdrivers were design to have a box end wrench to slip over the handle to be used for extra leverage. I have never forgotten that lesson and I actually cringed when I saw you do that expecting a hand to the back of my head. LOL

[@markeckman3662]

I've felt that thump too.

[@hillbillyrv]

LOL....Yeh I forget that a wrench will fit them.

[@Tom-Fisherman]

Freeze temp sensor opening. Unfortunately, diagnosing THAT is worse than the sensor issue.-------------5.2 Frost On Coil The formation of a light coat of frost is possible on a properly operating air conditioner, just prior to the cold (freeze) control shutting off the compressor. This is normal when the cold control function is correct; however, this may be an indication that the unit (1) is installed improperly, (2) maintained or operated improperly by the user, or (3) has a mechanical problem. The first two items listed above are the most frequent causes of frost formation, and they are NOT covered under the Dometic Warranty policy. Anything that restricts air flow will cause more frost on the coil.

[@hillbillyrv]

2 in a row?

[@iamoption11]

What was the problem and was that the fix i was waiting on a second video lol

[@hillbillyrv]

Coming soon.

[@davidcordle8702]

Sometimes those so called tech specialists will put you on a “Hummer” just to mess with you. You know, things that make you go Hmmmmm. They don’t care if you end up chasing your tail.

[@davidcordle8702]

Great idea turning on the radio and checking the battery

[@hillbillyrv]

Sometimes, yes.

[@jeffsteele1295]

Could be a heat generated problem. I had heard of problems with ac ripple that was hard as H*lLL to figure out. I hope this fixes the problem for you, or you might have to bring your sleeping bag with you lol .

[@hillbillyrv]

I told him that I wasn’t going to move in with him.

[@Yukonjackman1]

If you have worked manufacturing a build could be 10 , 25 or even 100 incorrect parts built then Sent to a customer.

[@hillbillyrv]

Wow