Sorry, this is a long post. I hope it helps someone with the same issue.
I have a 2001 Palomino Pop up with a Dometic RM2193 3-way refrigerator. Unlike bigger RV fridges, the 2193 is totally manual. There are switches for 12 v and 120v operation and a manual light propane option. It is up to the owner to ensure only one "way" is in operation at one time.
My fridge works great on 120v, but over the past year or so it would not cool when switched to propane. I picked up lots of advice from irv2 forums and these suggestions helped, but tonight I finally fixed the problem and wanted to pass along the solution. I am a do it yourself (DIY) guy so while taking it to the RV shop may be an option for some, this unit was not going to beat me.
Knowing that my fridge cooled quickly on 120v proved the ammonia refrigerant was fine, it was level, and had no other problems. My propane lit easily and continued burning when the button was released so the thermocouple was working. I could see the flame. It just would not cool. In my case, the fins inside the fridge did not cool at all.
There are maintenance instructions in the owners manual, http://bryantrv.com/docs2/docs/rm2193.pdf
and on this forum, but I was frustrated to read how these fixed others problems but not mine.
Here is the order I would suggest completing them in if your unit is 10 years old like mine.
1. Remove the burner cover by removing one screw and the sliding it to the left and out.
2. The burner located at the bottom of the flue pipe should be vacuumed out. I removed the one screw holding the burner to the flue (don't lose the lock washer). Gently slide it down and then out an inch or two. You are bending the propane supply pipe and thermocouple slightly with this procedure so go slowly.
3. While it is still out, clean the flue. Remove the Tee pipe at the top and remove the flue baffle. The baffle causes the hot flue gases to circulate and do their job. Some have found the baffle had fallen onto the top of the burner and this would definitely cause troubles. I cleaned the flue with steel wool - you can figure your own way to do this and not leave any behind. Vacuum some more. My baffle was in great shape, but the wire holding it was rusty so I sanded it smooth so it did not flake off and dirty the burner later on.
Re-assemble. I took care to ensure the burner was pointing straight up in the flue as I tightened the screw. I also pulled the thermocouple back out of the flame slightly is case it was reducing the effectiveness of the flame.
Most could stop there and be back in working order. But not me!
4. Get your propane system pressure tested. Mine was down to 9 inches of water column and had to be re-calibrated to 11 inches. If you are not a propane tech with your own meter, go to your dealer. From advice on this forum and Dr. Google, this should be done once a year and many RV dealers will test it for free. You might want to do this first actually, if you think it is taking longer to boil water on your stove than it used to.
That still did not solve my problem!
5. Clean the burner jet. The instructions are in the owners manual...snip...
To examine and eventually clean the burner jet, unscrew
the gas pipe union (K) and pull out the burner jet
Clean the jet by washing it in alcohol and blowing it
through with air.
NOTE: The jet fitted to this refrigerator is a size "45"
which is suitable for use on propane gas at 11
inches water column. The orifice in the jet is very
small and must never be cleaned by means of a pin
or similar instrument as this would damage the
orifice. It must only be cleaned as described above.
It is made from extremely thin metal so do not poke at it with a big tool or much force or you will
bend it or damage the precision hole. I read somewhere - don't use pressurized air to blow it out. The smaller end goes back in first and you will see it through holes in the side of the burner when it is seated properly. Again, gently encourage it to seat.
Still no joy for me!
When the fridge runs on 120v the row of fins at the back of the unit (at the top) were hot to touch, but only the first two or three fins were hot on propane. I borrowed a high temperature probe from work and found that on 120v the refrigerant tubing reached 270 to 290 deg F at the top as it bent left and was covered in about 30 fins. On propane it maxed out at 220 deg F.
I removed the burner jet again and looked at it with a magnifying glass only to find the hole was clogged with what looked like a burr of metal. I knew I had found my problem. I may have caused the burr to move in the way during cleaning which I had done before the pressure test. As a result, I suggest leaving the jet alone until all else fails.
So officially, step 6 is to carefully clean the jet again or purchase a new jet. I doubt they are expensive. Unofficially, I was able to remove the burr without damaging or enlarging the precision hole.
IT worked! The temperature reach 270 after an hour or two and was continuing to climb slowly. The refrigerator was cooling nicely according to my self-stick thermometer on the inside of the door.
They really are great little refrigerators. The Dometic in my 1980 vintage trailer worked well for 20+ years until I upgraded trailers.
We are off to a no-service camping area this weekend - just in time repair!