Dometic 3 way success story - Fiberglass RV


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Old 05-14-2020, 02:26 PM   #1
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Name: David
Trailer: 2013 Scamp 13 S1 BB
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Dometic 3 way success story

I am the 2nd owner of my scamp 13 and I have always been struggling with the 3 way refrigerator when running on propane. It would get cold but not quite cold enough and it would take a very long time. Recently, the performance got even worst so I decided to research the issue and try to fix it. Took everything apart, thermocouples, burner, orifice, gas valve, flue. Cleaned all the items and put it back together and still nothing.

Then i came across a post where someone said under magnification they saw a burr in the orifice hole. The orifice is so small its impossible to view anything in that hole without magnification. I pulled out my phone and was able to zoom in 10x and snap a few pictures of the orifice. Lo and behold I also had a burr in the orifice.

Thinking I had nothing to loose now since my orifice was not functioning anyway (a new one runs about $50 after shipping) i soaked it in a bit of diluted phosphoric acid and took an electric tooth brush to it. That didn't quite do it, so i took a tiny wire, 1 strand from a 28awg wire. Ran it through a few times, did the phosphoric soak again for a few minutes and finished off with the brush. Obstruction gone!

I put it all back together and my flame is now about 2x bigger/taller than before and the fridge has been dropping its temperature at a fast pace. I think i have found my gremlins!

Here are a couple of pictures:
Attached Thumbnails
obstruction.jpg   clean.jpg  

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Old 05-15-2020, 04:56 AM   #2
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congratulations on your success! i hope the "cure" is permanent. the only success i achieved with my dometic 3-way fridge with 8 years of trying to keep food cold was removing the thing and replacing with a 12v/120vac unit (no gas). it's a danfoss compressor unit and draws very little power.

p@
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Old 05-15-2020, 06:37 AM   #3
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Originally Posted by patrick crawford View Post
congratulations on your success! i hope the "cure" is permanent. the only success i achieved with my dometic 3-way fridge with 8 years of trying to keep food cold was removing the thing and replacing with a 12v/120vac unit (no gas). it's a danfoss compressor unit and draws very little power.

p@
Patrick this was my backup plan, but for now it looks like the domestic is staying. I went to a trip to Iceland a few years back and rented a camper with a waeco/domestic danfoss compressor refrigerated cooler, it was great, but they sure are pricey.
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Old 05-15-2020, 07:55 AM   #4
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I had Dometic Tech Suoport and two Mobile RV techs all tell me on the phone when describing the same problem that I needed a new motherboard @ $500-$700.

Finally checked the orifice and could see a small speck when holding up to the sky. Soaked in 99% isopropyl (only one available at Ace in March which turned out great to have a gallon for $25). Now will cool to 38 degrees on highest setting; previous was 42.

I cannot believe no one above asked whether the orifice had been cleaned. Five year old unit with no previous problems. I too was checking out new ones and had a quote for $1400. Fixing what ain't really broke sucks.
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Old 05-15-2020, 08:02 AM   #5
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Originally Posted by Osos1 View Post
I had Dometic Tech Suoport and two Mobile RV techs all tell me on the phone when describing the same problem that I needed a new motherboard @ $500-$700.

Finally checked the orifice and could see a small speck when holding up to the sky. Soaked in 99% isopropyl (only one available at Ace in March which turned out great to have a gallon for $25). Now will cool to 38 degrees on highest setting; previous was 42.

I cannot believe no one above asked whether the orifice had been cleaned. Five year old unit with no previous problems. I too was checking out new ones and had a quote for $1400. Fixing what ain't really broke sucks.
I agree, there isn't much information on this process online. People tell you to clean the orifice, but without actually magnifying it and looking for this problem, you could pull your hair out to no avail. This should be #1 thing to check on these dometic units. In my case mineral spirits soak didn't do it, because the burr was too large, and the acid and electric tooth brush finally helped to knock it lose.
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Old 05-15-2020, 08:05 AM   #6
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Quote:
but they sure are pricey.
yeah well, there is that. my casita 16'er came with a small dometic and the norcold (similar size) i bought was around $700. but, i figure i got 700 bucks worth of smiles already. and, the new one has a freezer! the one issue that still existed was the thing is too small for a half gallon of milk and other consumable liquids. well, since i was already in a spending mood i sprung for a gosun solar powered cooler. it uses a battery brick that uses solar charging. a full charges in the brick will keep the box running 16 hours (they say, but i can confirm a bit over 12). no ice involved. i've been using that cooler during the social isolation. for that i can power it on 120v and keep extra milk. oj, etc cold.
and there's room left over for a 12 pack of torpedo.

p@
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Old 05-15-2020, 09:14 AM   #7
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I understand that LP gas can contain some oil and crud that over time can collect and gum up the works. I wonder if (even without the burr) the collected crud could tend to reduce the flow to the burner and cause poor cooling?
Does anyone know the proper size orifice so that a proper cleaning tip could be used?
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Old 05-15-2020, 09:33 AM   #8
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Originally Posted by redbarron55 View Post
I understand that LP gas can contain some oil and crud that over time can collect and gum up the works. I wonder if (even without the burr) the collected crud could tend to reduce the flow to the burner and cause poor cooling?
Does anyone know the proper size orifice so that a proper cleaning tip could be used?
The dometic part number is 2922033044, at least for the rm2193, the description states it is a #45 orifice which doing some research corresponds to is .0820 It is a pretty small size, its not something that comes in most torch cleaning kits etc. I would be very careful sticking anything metal in there, i think a nylon tooth brush bristle would do a decent job of cleaning it. I think key is some solvent and then something to agitate it with.
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Old 05-15-2020, 09:39 AM   #9
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Right, it will depend on the fridge. Mine is old, an RM2301, and has the "ruby" orifice, which you absolutely don't want to clean with anything rigid. So far I've never needed to do more than soak it in alcohol (70% is often the most concentrated I can find), and blow it out with compressed air (one of those cans for cleaning keyboards etc).

But really, with how common a maintenance item this turns out to be, someone should make a brush specifically for cleaning the burner jet.

Somehow this spring my fridge is working well. Too well. My thermostat dial goes from "MAX" to "OFF". OFF being as low as the gas will go without actually turning the fridge fully off. Most days, I don't go above OFF, and in the morning I'm struggling to keep the temps in the fridge above 30. I have to keep opening the door to warm things up. We'll see how it does when outdoor temps rise. I don't believe that my fridge somehow worked out all it's kinks while it sat for the winter, so I figure it'll start to struggle eventually.

So far the weather has been mostly highs in the 50-60s, lows in the 30s. Perfect camper weather.
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Old 05-15-2020, 10:18 AM   #10
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Great information Gompka! Thanks. This is on my to-do list for spring cleaning.
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Old 05-15-2020, 10:47 AM   #11
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I've written this 3 times and lost it when other apps kicked so a long story short. Appliance orifice cleaners are available at supply house. Welding tip cleaners will work if they are the right size. Never go larger. A very small increase in diameter is a large increase flame. Debris does build up in lines and tanks. It will make it's way to your appliance. That is why mr. heater sells inline filters for use with refillable bottles. I haven't seen one, but inline versions are probably available. I'm going to check for myself.
I'm glad to see you got it going.
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Old 05-20-2020, 10:50 AM   #12
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Name: Dave
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Good read. I had a similar problem with my 3 way dometic.



It would have good trips and bad trips sometimes barely cooling at all and others working pretty good. When I finally pulled apart the gas line and orifice blew some compressed air down the line it puffed a big plume of black soot crap. Once all cleaned up it works like new.


Another tip I had from an HVAC tech. In expensive hotels they sometimes use dometic absorption fridges like RV's cuz they are silent. When the fridges stopped cooling properly they would flip them upside down then right side up each day for a week or so to remix the gasses. These fridges don't have a single gas/refrigerant in them like a regular fridge its a mixtures. I'm guessing bumping down the road probably does a pretty good job mixing everything up in our Rv's but just a thought for anyone whose has been sitting a long time.
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Old 05-20-2020, 01:43 PM   #13
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Dave you're right. A somewhat well known trick for these absorption fridges is to hook them to AC for a while, unplug and flip upside down. Some have had good luck with that method. Depends on what the problem is and how far along it is.
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Old 05-20-2020, 04:23 PM   #14
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My supervisor when I began working on a.c. units had been a tech in the 50's in the mid west. At that time there were a lot of the in homes and businesses in the area. When no other problem was apparent he would load the refrigerator in his truck on it"s back and ride it around with him for the day. He said it worked most of the time. It remixed and redistributed the chemicals.
He said to let the system settle for a day before starting it again. He new his business. He had started by working on cooling systems on ships during WW II.
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