Dometic 2551 Suddenly not cooling

[pcskier]

I am full-time for now in my 2014 23D(CB) while waiting to build a new house, and have often told myself how fortunate I've been for the past 21 months with no appliance issues, which sure are magnified when it's your permanent home. My luck might have run out.

I have a Dometic 2551 refrigerator, Propane or AC power. It has worked flawlessly since I bought the trailer in 2018 with lots of trips, as well as the last 21 months that I've lived in it. Mostly I've had shore power so I've run it on AC mode, but the propane option works great as well.

Yesterday I noticed the freezer had thawed completely, and there was zero cooling happening in the either compartment. It was like the unit was turned off. The unit was running on AC, and the light on the top control panel was on. The boiler was hot. I switched to propane mode and it immediately lit and the boiler stayed hot...I left it and went to bed to see if it was an issue with the AC mode.

This morning---no change, freezer and fridge not cool at all, and the boiler still burning hot. No visible signs of yellow residue suggesting a leak anywhere that I can see, or odors. The tube exiting the top of the boiler is hot, when it comes out of the fins/condenser, it's 'warm', and the absorption tubes that head back down to the bottom of the unit are completely cool...I think they are supposed to be hot?

Given that there is power to the unit, and the boiler heats both on AC and Propane...but there is no cooling...and I mean NONE happening...does this point to a failed cooling unit, or is there a possibility of an issue with one of the two control boards? My thoughts are that if the unit turns on and heats the boiler in either mode, as long as the boiler is on, the electronic controls are working properly, and the problem is the cooling unit which I can replace, but that's really a challenge given my living situation, and it's winter here in Park City Utah.

For what it's worth, it's not a leveling issue, that's dead on. It was down to below zero the past few nights (only down to 26 last night though) but that shouldn't matter. It's not a cooling fan/ventilation issue, that was still running this morning, and with the low winter temps, def no problem. Plus the unit worked great all summer when it was 90 degrees out.

Replacing the cooling unit would be a real bear of a job to remove the fridge and work on it in my storage unit in the cold. It also seems hard to find a new RM 2551 as well, most dealers don't even show them as an option.

Any ideas on if there is more for me to explore before deciding on replacing the cooling unit or getting a new fridge, would be appreciated.

Or maybe it's time for a compressor fridge but that's a topic for a different thread.

[ITSNO60]

How cold is it where you are? Read below: (credits to the late Gary Bunzer the RV Doctor)

[pcskier]

Originally Posted by ITSNO60

How cold is it where you are? Read below: (credits to the late Gary Bunzer the RV Doctor)

It got down to -6 F a couple nights ago, and about 0 the night after. Teens during the day. Yesterday in the 30s and down to about 30 overnight. Never an issue last winter, and I'm in an RV Resort with dozens and dozens of various rigs here for the winter, and nobody I've spoken to has had any problems.

Not to say the colder temps could impact performance, but my cooling has completely stopped--the boiler appears to be operating, too hot to touch the pipe line coming out of the top for more than a second or two--but there is no noticeable cooling impact in the freezer or fridge, and the absorption line heading down to the bottom are cool to the touch--I think they are supposed to be hot, or at least very warm still?

[ITSNO60]

Originally Posted by pcskier

It got down to -6 F a couple nights ago, and about 0 the night after. Teens during the day. Yesterday in the 30s and down to about 30 overnight. Never an issue last winter, and I'm in an RV Resort with dozens and dozens of various rigs here for the winter, and nobody I've spoken to has had any problems.

Not to say the colder temps could impact performance, but my cooling has completely stopped--the boiler appears to be operating, too hot to touch the pipe line coming out of the top for more than a second or two--but there is no noticeable cooling impact in the freezer or fridge, and the absorption line heading down to the bottom are cool to the touch--I think they are supposed to be hot, or at least very warm still?

Well temps at and below zero are where some experience no cooling, if the solution in the coils begins to freeze it will not work. I would try hanging an incandescent bulb in your outside compartment. Some fridges have a cold weather switch but from my understanding all it does it keep the interior light on which provides enough heat so the unit runs continuously and doesn't get a chance to freeze up. Once the unit reaches temperature it cycles off and then is susceptible to freezing. Maybe yours was not opened for a long enough period that it shut off during the cold night and the solution has started to solidify and with daytime temps below freezing it can't thaw. Maybe a small heater to get it going?
When the solution in the coils starts to freeze it gets slushy and then all cooling stops.
And yes the return line normally feels warm, everything you described points to no circulation due to frozen or slushy solution.

[richard5933]

Any evidence of leaking from the cooling unit? Yellow powder under it?

[pcskier]

Originally Posted by ITSNO60

Well temps at and below zero are where some experience no cooling, if the solution in the coils begins to freeze it will not work. I would try hanging an incandescent bulb in your outside compartment. Some fridges have a cold weather switch but from my understanding all it does it keep the interior light on which provides enough heat so the unit runs continuously and doesn't get a chance to freeze up. Once the unit reaches temperature it cycles off and then is susceptible to freezing. Maybe yours was not opened for a long enough period that it shut off during the cold night and the solution has started to solidify and with daytime temps below freezing it can't thaw. Maybe a small heater to get it going?
When the solution in the coils starts to freeze it gets slushy and then all cooling stops.
And yes the return line normally feels warm, everything you described points to no circulation due to frozen or slushy solution.

I have to admit the cold temps made me wonder. But it was in the 30 yesterday and is 40 degrees today, plus with me leaving the unit 'on' so that the boiler is heating, the compartment is warm enough that the fan was even running. And none of the tubes feel cold at all to indicate they are frozen. But...I will try heating things up as you suggest just to see.

[pcskier]

Originally Posted by richard5933

Any evidence of leaking from the cooling unit? Yellow powder under it?

Non whatsoever, and I've looked very closely.

[ITSNO60]

Keep us posted. I also read where someone was able to get theirs circulating by vibrating the coils.

[pcskier]

Originally Posted by ITSNO60

Keep us posted. I also read where someone was able to get theirs circulating by vibrating the coils.

Thanks, I will. I've blown an entire day on this. It's so warm today and in the compartment, I'm sure nothing is frozen. But whether on propane or electric, the boiler is hot and the tube leaving the boiler is hot. So there must be a blockage, or a leak. I almost wish I'd see some yellow powder or smell ammonia so that I would KNOW it was the cooling unit. I can get a new one for around $550 but it's taking out the fridge and having to disassemble it to remove the cooling unit and replace with new one...is just so daunting. Not really any room to do it inside my 23d, next option is to go to my unheated storage unit and do it there in the cold. Likely a full-day project to boot. So I wish I could confirm it's the cooling unit, but I really don't know what else it could be. I unplugged the thermistor cable from the board just to be sure that wasn't bad an sending the board the wrong message, so it ran with no regulation. Still no cooling. Not just limited cooling, but absolutely none. Room temperature in freezer and fridge. Such a hassle

[pcskier]

In case any of you can help determine if it's my cooling unit that is clogged or has an unobserved leak, here is some info:

I ran it on propane all night and most of today...the chimney tube gets quite hot, and the tube coming out at the top is too hot to touch...so far so good?

Then where the tube makes a 90 degree turn to enter the condenser fins, it's cooler to where I can keep my hand on it.

By the time it exits the fins, it is just warm; and then as it coils it's way back down to the absorption canistor, the tubing is cold...shouldn't it be hot, indicating it's drawn heat from the fridge?

I am ready to just order one of the Amish rebuilt cooling units for $535 but wish I could be absolutely sure that the cooling unit is my problem.

To review: all worked great until yesterday or maybe the night before; then, suddenly even though the chimney gets what seems like normal heat (I am used to feeling it whenever I want to make sure my fridge is on), I have absolutely NO cooling in the freezer or fridge compartments. They are both room temperature and the back walls as well.

Should I just hope for the best and get a new cooling unit and go through the misery of removing my fridge in the middle of winter while I'm living in the trailer, and change out the cooling unit? There are no obvious signs leakage or ammonia odors. I'm thinking there must by a clog that's developed, given the operation of the boiler but zero cooling.

[richard5933]

If the flame is burning or the electric is heating but the unit is not making cold, the my assumption is a failed cooling unit. Mine had no powder inside to show as evidence, and it only made some faint gurgling sounds when running.

Before ordering the cooling unit I spoke to the guy from rvcoolingunit.com and ran through some confirmation steps first.

My trailer is a 25-ft unit, only slightly larger than yours. With the tables folded up I had no problem laying the fridge down on the floor in the living room on top of a moving blanket, and I was able to do the swap in there with little problem. You'll need a helper to lift the old cooling unit and reseat the new one unless you levitate well.

Took me about 8 hours, but I worked at an OCD pace that day making sure that every detail was checked three times, all the compartment sides were clean, and that all the caulking was redone. Probably would take a normal person less time than that.

Watch their install videos and then make a decision.

[ITSNO60]

Before you write it off can you hook up and take it down a bumpy road?

[pcskier]

Originally Posted by ITSNO60

Before you write it off can you hook up and take it down a bumpy road?

Not really an option...I'm set for winter with skirting installed and the sides of that pretty well snowed/iced in. It would be a real ordeal. I was considering taking it out and doing what some say has worked...laying it on it's sides, and upside down overnight to get any obstruction moving again...but some say if it works, it's a temporary fix, others say it's worked for years after that. My inclination, if I got through the trouble of taking it out, would be to just spend the time and money and go ahead and change out the cooling unit. These Amish units are supposed to be way better anyway.

[pcskier]

Originally Posted by richard5933

If the flame is burning or the electric is heating but the unit is not making cold, the my assumption is a failed cooling unit. Mine had no powder inside to show as evidence, and it only made some faint gurgling sounds when running.

Before ordering the cooling unit I spoke to the guy from rvcoolingunit.com and ran through some confirmation steps first.

My trailer is a 25-ft unit, only slightly larger than yours. With the tables folded up I had no problem laying the fridge down on the floor in the living room on top of a moving blanket, and I was able to do the swap in there with little problem. You'll need a helper to lift the old cooling unit and reseat the new one unless you levitate well.

Took me about 8 hours, but I worked at an OCD pace that day making sure that every detail was checked three times, all the compartment sides were clean, and that all the caulking was redone. Probably would take a normal person less time than that.

Watch their install videos and then make a decision.

Thanks for the intel, that's the kind of info that's super helpful...that your cooling unit was bad and there were none of the telltale signs. Was yours just cooling poorly on gas and/or electric, or just suddenly completely quit with absolutely no cooling, like mine?

I've exchanged a couple emails with him, and he suggested I recheck level (I set up for winter November 1st and was very careful with leveling for the 5 1/2 months I'd be stationary) and that I do the test where I plug the electric element directly to a 120v source and measure the power draw/heating via an amperage clamp. But I just don't get the point of that, as the boiler gets hot on electric and propane, but no cooling at all from either. Surely one of the other could go wonky but not both at the same time. And even if both happened to suddenly not be hot enough, there would be *some* cooling, but there literally is none.

So even after taking yours out and disassembling the chimney to expose the boiler and burner tube, there were so sign of leakage anywhere? I'm really leaning toward believing that's my situation, though mine must have been catastrophic...I had great cooling one day with frost in the freezer, then absolutely none the next and completely thawed, yet no ammonia smell or anything. Perhaps a chunk of material that had built up over time broke free and basically gave the unit a sudden heart attack, basically?

I think if I take my lounge cushions out I actually would be able to lie it on there after putting some towels down and do the work inside. That would help a lot.

[richard5933]

Mine had no symptoms other than it didn't make cold. The tubes heated up, but no cold. It was like that when I bought it, so no telling how long it was out. But, I saw no signs anyone had ever cleaned behind the fridge, yet there was no telltale yellow powder.

The new unit from rvcoolingunit.com really works well and I was impressed with how thorough they thought through the process.

Lay in a supply of disposable gloves. The one annoying part was getting the spray foam on the edges of the cooling unit. You have to put the foam on before inserting it into the fridge, and it takes some coaxing to get it to stay put. This is where gloves and a helper are key. I did a dry run first to make sure we could land it squarely in place once the spray foam was in place.

[pcskier]

Originally Posted by richard5933

Mine had no symptoms other than it didn't make cold. The tubes heated up, but no cold. It was like that when I bought it, so no telling how long it was out. But, I saw no signs anyone had ever cleaned behind the fridge, yet there was no telltale yellow powder.

The new unit from rvcoolingunit.com really works well and I was impressed with how thorough they thought through the process.

Lay in a supply of disposable gloves. The one annoying part was getting the spray foam on the edges of the cooling unit. You have to put the foam on before inserting it into the fridge, and it takes some coaxing to get it to stay put. This is where gloves and a helper are key. I did a dry run first to make sure we could land it squarely in place once the spray foam was in place.

Awesome thanks! Meanwhile, on rvcoolingunit.com I found a page of different tests, and this one stood out in a section on 'touch' testing:

"When a cooling unit malfunctions due to a blockage, the boiler section may be too hot to touch and the absorber will be relatively cool. Any blockage reduces the free flow of the solutions and will inhibit or completely prevent proper cooling operation."
This describes mine perfectly. The boiler tube is very, very hot, and the absorber lines that snake down the back to the absorber canister are cool to the touch.

I am touching base with him on this to confirm but it looks like this project is in my future. I'll do a post on it after I'm done.

[xyzabe]

If you are going to consider replacing the cooling unit, check out https://jc-refrigeration.com/

They make a freon compressor unit that will replace your absorption unit. You can get it AC or DC and not use propane. Excellent choice because it does not require the unit to be level (like absorption) and can work with solar if you have it. We are looking at changing out our absorption system to extend our boondocking time. Also, you don't have to turn off the refrigerator if running propane while fueling or going through tunnels. And you eliminate the fire hazard from overheating and the toxic fume hazard if you have an ammonia leak

A lot less expensive than replacing the whole unit. And much safer too.

[pcskier]

Well.

I went to bed last night, resigned to order a replacement cooling unit today. I turned off the fridge, as there was no point in running it any more. Pretty sure the problem is a blockage.

Today...just for fun, having let it sit all night turned off, I turned it back on. I wondered if maybe, just maybe, turning it off and shutting down the boiler might somehow allow things to cool and move around in the tubes.

Within an hour, the back of the freezer had a sheen of ice on it. What?? Put a small dish of water in the freezer, and a glass of water with a thermometer in the fridge. After a few hours, the fridge was 39 degrees, and the water in the freezer was frozen solid. Crazy!

I can only guess that the fluids were able to move around a bit without the boiler trying to force fluids into the lines, or something. So we will see...maybe I've gotten lucky for just a day...or a week....or month....or years. We will see. If it happens again, I'll come back and update this thread, but for now, all is well in the kingdom. Knock wood!

[ITSNO60]

Originally Posted by pcskier

Well.

I went to bed last night, resigned to order a replacement cooling unit today. I turned off the fridge, as there was no point in running it any more. Pretty sure the problem is a blockage.

Today...just for fun, having let it sit all night turned off, I turned it back on. I wondered if maybe, just maybe, turning it off and shutting down the boiler might somehow allow things to cool and move around in the tubes.

Within an hour, the back of the freezer had a sheen of ice on it. What?? Put a small dish of water in the freezer, and a glass of water with a thermometer in the fridge. After a few hours, the fridge was 39 degrees, and the water in the freezer was frozen solid. Crazy!

I can only guess that the fluids were able to move around a bit without the boiler trying to force fluids into the lines, or something. So we will see...maybe I've gotten lucky for just a day...or a week....or month....or years. We will see. If it happens again, I'll come back and update this thread, but for now, all is well in the kingdom. Knock wood!

I was actually wondering if you had tried shutting it off for a while, I should have spoke up! I had a feeling that we would be hearing from you eventually that it started working, fingers crossed but betting it will be fine..

[pcskier]

Originally Posted by ITSNO60

I was actually wondering if you had tried shutting it off for a while, I should have spoke up! I had a feeling that we would be hearing from you eventually that it started working, fingers crossed but betting it will be fine..

Well thanks for those unspoken positive vibes...they surely helped!

I thought I was being ridiculously optimistic, and was just dreading the prospect of having to remove it and install a new cooling unit, what a way to spend a day. But I realized that even though there was no cooling at all, it had not been turned off...and maybe...just maybe...doing so would miraculously allow things at the boiler end to cool and move around in the tubes. So when I turned it on and an hour later felt the frost in the freezer...I was elated. Something was up for sure, but with any luck, there won't be a repeat anytime soon. I do wonder if the -6 temps the other night still had something to do with it.


Anyway...onwards, for now!