Servicing a Dometic RM2333

[Larryjb]

I will assume many other Dometic models will be similar, and perhaps even the Norcold ones. I had a yellow flame, not igniting easily, and not cooling very well. I decided to see what I could do. Many thanks to Dick (commodor47) to helping me get started on this, especially for his find of a source of service and user manuals for older fridges ( http://bryantrv.com/docs2/ ). Look in the subdirectories, or go to the home page. However, not all manuals are accessible from the home page. The one for the RM2333 had to be dug up from the files.

So far, this is what I've done. I'll continue this as I complete the project.

1) Remove the upper fridge access panel from the street side of the trailer. From here you can see the top of the flue and baffle. The baffle reflects the heat from the flame to the sides of the flue where the ammonia mixture is heated and vaporized.


Baffle removed:


2) Remove the lower fridge access panel. This is where the manifold is located. You must first remove an inner metal shield:


and then a second shield:


This second shield is a little tricky to remove. If you look closely, you'll see a couple of notches on the top of this shield that keeps it secured in place. It takes some wriggling around, but it will come out. It takes two hands at both ends of the shield.

I'll put part 3 in the next post.

[Larryjb]

3) Unscrew the burner assembly. I needed a Phillips bit on the end of a ratchet drive to get it in the space.


4) Examining the baffle and burner:
The burner shows a lot of surface rust. I am soaking it in toluene, but I'm sure it's a futile effort as toluene won't touch rust. I could soak it in an acid solution, that that would erode material away. No matter what I do, material will be eroded away because it is rusted. I need a new burner.

The baffle also shows rust. However, because the purpose of this is to reflect heat to the boiler part of the fridge, I can probably get away with polishing it up. I will check the price of a replacement first, though. A new one would have a much better polished surface than I could do myself.

[Larryjb]

Once I get replacement parts, I'll show the assembly and adjustment, according to the manual specs. After that, I'll look into the DC and AC cooling modes. I suspect there are a few problems there too, probably mostly related to poor electrical connections.

[grubbyjeans]

Has this refrigerator been sitting for an extended period? I ask because that too can affect the cooling capability of the unit.

We bought a 1985 Apache in 2011 that had been used for temporary living quarters for a while. It had been well cared for and return to the road wasn't much trouble except for the refrigerator.

It would light easily enough, but just wouldn't cool. Someone in the Apache community suggested that I needed to rotate the refrig. over a period of several days. It seems that the ammonia crystallizes over time when not in use, causing loss of cooling.

Sure enough, I took it out and set it on its side for a few days. I continued the process for about a week and half, letting it sit upside down, then on its other side. I fired it up and noticed an immediate improvement.

I repeated the process three or four times and each time it improved. While I had the unit out of the trailer I replaced the door gasket and put new insulation on the flue and cleaned and repainted.

When we sold the trailer in 2015 it was working perfectly.

[Larryjb]

Interesting comment about crystallization. I'm not sure what would crystallize though. The chemicals in the system are water, ammonia, and hydrogen gas. The only possible crystal I can see from this is ammonium hydroxide, which melts at -108 F.

see my response in post # 7

Obviously, taking it out and rolling it around must have done something.

In my case, I don't think the propane mode was used much. The result is rusting of the burner and baffle. I never took a picture of the flame, but it was very yellow. These fridges are very sensitive to having a good blue flame, so this is my main issue.

[Bill]

There is quite a bit of information on line about the need to rotate a refrigerator. Although I was skeptical when I first ran into the idea several years ago, there is enough reported experience, from believable sources, that I have come to believe in it. The operations is usually called "burping" the refrigerator. There are several theories about why burping is necessary - what happens inside the coolant lines. Chemicals stratify, crystals form, air bubbles and vacuum blocks, etc. There seems to be little agreement on what causes the problem, but all agree that burping fixes the problem.

Bill