Dometic RM 66F

[manda1215]

So, I've been flipping through the posts, and I apologize if this is already answered elsewhere, but I couldn't seem to find quite what I was looking for.

My wife and I live full-time in a 1976 Argosy 24 "Juniper". When we moved into it in February the fridge (Dometic RM66F) was not working on electric, but was working fantastic on propane. As the outside temps in Texas started to work their way up, the fridge has had a more and more difficult time keeping up. Now, it sort of gets cool (maybe) but certainly not like it was doing this winter. I took it to a local RV shop this morning, and after explaining the situation was told that I need either a new fridge or a new cooling unit. Based on what I've read on these forums, I'm not quite ready (mentally or financially) to throw in the towel just yet.

I'm fairly new to this game, and my wife and I are on the slow road to renovation with Juniper . Any counsel would be greatly appreciated. I can post pics if that will help.

-MB


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[TG Twinkie]

It could be a number of things.
Poor airflow across the back of the refer.
Exhaust stack plugged with soot
Lack of the proper propane pressure. 11" of water column is the correct pressure.
Plugged burner.
Plugged orifice
Plugged filter in the propane line.
If you have not lost the ammonia charge. Chances are it is fixable.
Do you have the thermostat set to the lowest temp setting?
Post a pic if the controls.

[manda1215]

I don't think I've lost the ammonia charge. Nothing has given me any indication that I have (though I wouldn't really know what to look for. No yellowing, no smell of ammonia, though).

I haven't had it set to max cold in a while, but when I did it still wasn't cooling properly. I'll give it a shot tonight, though.

I've tried looking in the stack for blockage of any kind, but I haven't been able to get a really good look because of the bend of the stack. Here are a few pictures.

[idroba]

I have had two of those, and I would suggest you take the burner cover off and use compressed air to completely clean out the burner screen and burner tube. Very often they get filled with rust and although there is a flame, it will not create the heat needed to do proper cooling.

In addition, check your gas pressure. It needs to be 11" WC. If it is low, your burner will not produce enough heat.

And remember, the capacity of all propane refrigerators is reduced in hot weather. Yours is old, even things like the door seals could be leaking allowing extra heat and moisture into the box.

[TG Twinkie]

Can you see the ground when you look thru the access door on the outside of the coach. You can check the vent stack with a flashlight at night by shining it from below. Light should appear under the rain cap. There should be a double screen which allows air to flow up the back of the refer thru the floor.
The best way to do a complete check of the system is to remove the refer from the coach. Then connect it to a propane source using a regulator.
On my refer the burner would not go up to full flame. Turns out that the safety valve was also defective and would not shut the gas off completely when there was no flame present. I also found the inline filter to be plugged and saturated with the liquid used to give propane it's smell.
I was not able to locate a low pressure filter unit. However I did remove the filter medium from the old filter cartridge. I then used a cigarette filter for the new filter medium.
It is virtually impossible to get to the (cork screw) defuser in the boiler stack from the access hole in the coach. It is easy when the refer is out of it's location in the coach.

[manda1215]

Thanks for all the assistance!

TG Twinkie, I can see the ground from the back side of the refrigerator, but I'll take a look tonight with a flashlight out the top.

I'm going to be out of town next week, but I will try to get the refrigerator out to get a closer look as soon as I get back. Those of you with experience, is this a pretty straightforward process? I assume that it will be pretty time consuming, I just want to know if there are any special things to be mindful of. Also, I checked last night and the fridge is pretty much perfectly level (off level by less than 1°). I'll continue to post as I go through this process.

Again, thank you all for your help!


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[idroba]

I would agree that removal for a complete cleaning is a good idea. At the same time, you might want to check out the electrical side of the system to see if you can get that operational. The heating element especially would be suspect.

Removal is sometimes not too hard, but other times is a really big PITA. In my '74 Argosy 20', when replacing the refrigerator, I also re built the cabinets and countertop, so I had everything apart anyway, which made things easier. Still, you will need to get to the lag screws which hold the refrigerator to the floor. There are at least 3 of them, maybe all four corners are held down. Wrenching in very tight conditions is not easy, but it depends a lot on just how the entire system was assembled in your specific trailer. On mine, the refrigerator set up on a metal pedestal about 4 inches, and the pedestal was what I removed from the floor, still attached to the refrigerator.

You may find that removal of the countertop and all that involves, is still worthwhile. As mentioned above, so much of my cabinetry was loose and tired that I found it easier to do a rebuild of that stuff at the same time I replaced the refrigerator.

[manda1215]

Update on this topic: My wife and I were gone this past week, but I had the refer on gas and set to max temp. While it hasn't been too warm where we are, the refer seems to cooling at least semi-adequately. I'll know for sure today with our first HOT day in a while.

However, before undertaking the task of removing the refer, I decided to see if I could get it working on electric first. I knew already that the outlet inside the refer compartment was getting power. So I decided to check first for continuity of the power cable. Ground was good, neutral was good, but no juice on hot. So, I pulled the cable out and checked for continuity again. Looks like it was just a dirty connection point. I've cleaned it, but I haven't checked all of the other electric components for continuity just yet.

Which brings me to the next question. If continuity is good all around, how long will it take before I know that the refer is working on electric, if it's already pretty cold on gas?

Thanks all for your help!!!


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[idroba]

It will warm up in a few hours if it is on electric and that is not working. I would guess 2 to 4 hours.

[manda1215]

So, I did something a little bone-headed which is why I'm now asking this question. In the process of cleaning the screws that hold the power cable to the board, one of them dropped in the grass, and after about 30 minutes of searching (most of that time with a powerful magnet), I finally decided maybe I should just try to find the screws and replace them all, just to be safe. Well... that has proved a bit more difficult than I thought. After talking with Dometic and getting a manufacturer's parts list, I know now that the screw I'm looking for is a 3.5x5mm zinc plated screw. However, it's labeled as KCS, and I'm wondering if anyone can help me figure out what that is (and where to get one).

I've been scouring the interwebs, but I've sort of hit a dead end.


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[TG Twinkie]

Was the refer still in the trailer? If so, you might look in the fresh air vent screen. In the floor below the terminals. Or around the edges of the vent.
The screw may be brass, a magnet won't pick it up.

[idroba]

You can usually get metric screws at a full line hardware store like ACE or True Value.

[Howard L.]

As well as Ace and True Val, many on line sites also. If original was stainless, no magnet pick up either. Use stainless with a dab of Never-Seize on the threads for all future fasteners to aluminum.


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[manda1215]

I apologize, I haven't been able to stay on top of this as much as I would like. Through a buddy of mine who works in manufacturing, I was able to 100 brand new screws for $4, haha.

I replaced the screws yesterday, the refer is now getting power on electric, however, it is still not cooling. It still works on propane, although, same issues as before (cool, not cold). Once it starts to cool off again here, it shouldn't be as much of an issue.

In any case, now that I've established that power is getting to the refer, can anyone advise where I should go from here? I feel like knowing that it works on propane (though it could probably stand to be serviced), should be an indication that it's working overall, and now it's just a matter of isolating the electrical issue. Or are the two completely separate?

Thank you all again for your help!

[idroba]

Originally Posted by manda1215

I replaced the screws yesterday, the refer is now getting power on electric, however, it is still not cooling. It still works on propane, although, same issues as before (cool, not cold). Once it starts to cool off again here, it shouldn't be as much of an issue.

In any case, now that I've established that power is getting to the refer, can anyone advise where I should go from here? I feel like knowing that it works on propane (though it could probably stand to be serviced), should be an indication that it's working overall, and now it's just a matter of isolating the electrical issue. Or are the two completely separate?

Thank you all again for your help!

On electric, is the chimney getting warm after a few hours? If not, you still have some electrical issue to deal with. If you have a Kill A Watt meter or can buy one (about $25 at many hardware stores) you can plug the refrigerator into it to confirm that it is drawing power. It should read in the 200 to 300 watt range.

The propane flame system and the electric system on your refrigerator are completely separate. If it cools on propane, it should cool on electric. Each is simply a different source of heat for the refrigeration cycle. But, both must provide heat, and enough of it, to make the cycle work.

[TG Twinkie]

The heating element may be bad. It is relatively easy to replace. The burner may also need to be serviced.