Dometic fridge RM2652 tripping thermal sensor

[rvman69]

Hello all, my Dometic RM2652 in my 99 Travelmaster class C RV was in my level shop hooked up and running good. I went out one day after we had a pretty bad storm and our electricity went off and back on about 5 times in a short period of time. Then it stayed off for about 36 hours. I noticed that our fridge power light was not on the fridge. So I turned the fridge off and reset the thermal switch on the heat unit. I went back in and turned fridge on. The power came on and the auto light was on. So I thought well the storm just threw the thermal sensor. So I turned the fridge off so I could clean it thinking it was fine. Well today I went out to turn the fridge on to get ready to go camping at the end of the month. When I turned it on the the lights came on the control panel as it should. It was on for a while then later I noticed the lights on the fridge were off. I went back to the thermal sensor and it was thrown again. I reset it again and it did the same thing. The heating element is getting hot. I do not think the cooling unit is bad but not positive. I do not see any yellow or green looking stuff around the heat unit. Is there anything else I should check that could be making the fridge not operate correctly? Could it be that the thermal sensor switch is just bad? Would appreciate any help. Is there a way to post pictures on here? I was going to post a couple so you could see there seems to be no yellow or green looking stuff. Thanks

[rvman69]

Has anyone bought a remanufactured cooling unit from cooling unit warehouse? If so what was your experience. Thanks

[rvman69]

Also where would be the best place to look at the amish rebuilt units? Thanks

[rvman69]

Ok a rebuilt cooling unit it is. Will the rebuilt units that come with new flue have the place for the thermal breaker? Or do you have to make the spot. Thanks

[JBarca]

rvman69 wrote:
Well I had the camper plugged in out in my shop since last November after last camping with the fridge on. The propane was on also. So I wonder if the unit had leaked out some. Then when the storm took out our electricity the burner kicked on and caught the tube inside on fire. Wonder if that could have burnt some of that stuff up maybe clogging that tube up some. Then when electricity came back on it got to hot and thermal fuse popped out. Just an idea. Thanks

I'm not sure about the fire part, I have never seen the fluid burning outside to know what it looks like when burning. I have only had to deal with cleaning up the mess of leaked-out fluid when installing a new cooling unit.

I will say that the controls' stack safety sensor (thermal disk switch) is not auto-resettable. You have to push the button to reset it. The controls do not care if you are on gas or electric; the sensor will trip the same. It might trip faster on gas, but if it tripped when you were on electric and the power went out, the gas would not fire off as the safety switch would have been tripped already. If, by coincidence, the gas did fire off and the switch got tripped, it would shut the gas down, never to come back again. If a burning glob fell, it should have landed on the gas burner tube, and you did not report the burner tube had any large glob in it. The system may have started leaking over the winter, but once they start leaking, they are not cooling right, and the safety should have tripped sooner or later.

Your post is a good learning one, for me, anyway. The cooling coil unit I had to replace failed overnight and never tripped the safety sensor. The fridge was on in my shop as the camper was there for water damage repair. When I walked in the following morning, the shop smelt like a big ammonia bottle. In this case, the fluid leak was a big one, it let out the coolant quickly, made a big mess, a big stink, and I caught it before the system tripped the safety sensor. The fridge temp could have been satisfied and not called for cooling.

John

[dougrainer]

Yes, you have a leaker. New cooling unit(rebuilt amish). Attempt to remove the 120 element after it has cooled down. They sometimes will not pull out. If it comes out. Great. If not, Then order a 120 element when you get the cooling unit. Be advised on Dometic, you do NOT get a new Baffle. You have to transfer from old cooling unit. Doug

[JBarca]

rvman69 wrote:
John, Thanks for the photos and information. Well I have had it plugged in for 6 hours. All of the lower pipes I can reach 6 thru 12 on your diagram are still cold to the touch. So there is no movement in the cooling unit is this correct? The flue is so hot all I can do is tap it with my finger with out get burned or blistered. I am pretty sure it is not working at all. I got a feeling I am going to be ordering a cooling unit. I know it takes a long time for it to start cooling down inside fridge and freezer but it should start circulating in 6 hours correct? Just as a note after 6 hours the temp in the freezer and fridge did not drop at all. Thanks

Hi,

As you see from my data, point 10 on the cooling unit started at 53F, and approx 1 1/2 hours later, point 10 was close to 106F on a working fridge with only 1 gallon of ambient temp water inside the fridge.

At approx 5 1/2" hrs later from starting, the yogurt cup of water in the freezer was frozen solid. The cup is about 1 1/2" deep water.

The above readings are from cycling on and off of the electric heating element from the control system.

If you have been on for 6 hours non-stop heating element and point 10 is still cold, well, the fluid is not circulating.

Point 1, which is the sleeve of the electric element, gets up into the 600 to 700F degree area. The boiler tube with moving fluid, I suspect, is less but still very hot and could be in the 450 - 550 range. The metal shield over the insulation gets convection heating, which is where the thermal disk switch sensor is mounted and shuts the system down. I am not sure what setpoint that trips at.

It could also have partially blocked flow internally and just now starting to leak. If the fridge is run off level for a good period of time or multiple smaller amounts of time, the fluid gets burnt and starts clogging until there is no flow. It's an accumulative issue that once the fluid is burnt, that area will never get better unless the coil is cleaned out during a rebuild.

Again, curious about what Doug will say, but the test so far does not look good; your cooling unit is not working and very possibly leaking.

I will say this, if you change the cooling unit, plan on changing the electric element at the same time. They are not that expensive, and they do go bad over time, they short out inside the element and trip any GFIC the camper is ever plugged into.

John

[enblethen]

That sounds likely to me!

[rvman69]

Well I had the camper plugged in out in my shop since last November after last camping with the fridge on. The propane was on also. So I wonder if the unit had leaked out some. Then when the storm took out our electricity the burner kicked on and caught the tube inside on fire. Wonder if that could have burnt some of that stuff up maybe clogging that tube up some. Then when electricity came back on it got to hot and thermal fuse popped out. Just an idea. Thanks

[enblethen]

Looks like you had a fire in the tube. Clump of material could be ammonium fire residue.

[rvman69]

John, Thanks for the photos and information. Well I have had it plugged in for 6 hours. All of the lower pipes I can reach 6 thru 12 on your diagram are still cold to the touch. So there is no movement in the cooling unit is this correct? The flue is so hot all I can do is tap it with my finger with out get burned or blistered. I am pretty sure it is not working at all. I got a feeling I am going to be ordering a cooling unit. I know it takes a long time for it to start cooling down inside fridge and freezer but it should start circulating in 6 hours correct? Just as a note after 6 hours the temp in the freezer and fridge did not drop at all. Thanks

[JBarca]

Curious about Doug's response to your last pics. Here are my thoughts.

Stop poking at the baffle; you have very little rust in the burner tube, and poking at it can damage or, worse, unhook the baffle from the draw rod. There does not look like any evidence of mud daubers' nests.

The yellow in the burner tube and the glob under it doesn't look good. As you heat the boiler tube with the electric element, the metal expands, and any thin crack in a weld or fatigued joint can start to open, allowing the coolant to start to leak. You may be at the start of the cooling unit failure.

Do you smell any ammonia type of scent when the unit is heating?

Doug has seen more of these failures than I have, and he has the 24-hour full-on electric element test he can report better on than I can.

These pics are of an actual 2004 RM2652 undergoing restoration for water damage, and I service the appliances. They may help you understand what is going on behind the burner insulation. This fridge is a working one, not a failed one.

I did tests to see what the boiler area and the cooling coil temps were at to see what normal is supposed to be.

This is the raw cooling coil out in the open.




Here is the operation test. The fridge is running under its control system, and I recorded readings at the l location until the unit cycled off the electric element.


Here is location 1, the steel sleeve the electric element is in.


Here is the first set of data.


The second test with more data. I had a cup of water in the freezer and a gallon jug in the fridge as a load for the refrigerator to work on. The remote thermometer is inside the fridge
compartment


Hope this helps

John

[rvman69]

Can it mess up the heating element if it is not operating and getting to hot? Well I might have my answer already. I moved the burner assembly out of the way so I could get to the pipe the baffle is in good. When I stuck a wire up in there it sounded like I got the baffle to rattle some. I could not get anything out of there. Then I hooked the heating element to extension cord. After it had been plugged in about an hour I ran that wire back up in the baffle pipe. Here is what I got to fall out. If it is bad I don't want to mess up the heating element and have to replace it also. Also it looks messed up in that pipe. See pic. Please let me know your thoughts. Thanks

[dougrainer]

rvman69 wrote:
So I guess I should be able to determine fairly quickly if the unit is at least circulating. All of the circulating coils should start warming up. Is this correct? If the circulating coils do not start getting warm after a while then it would mean that either the stuff inside has leaked out or there is a clog in the system. If that is the case there would be no reason to leave it on 24 hours. Is my assumptions correct? I guess then it would be time to order a cooling unit. I hope I dont have to but you have to have a fridge.

There is NO danger to running on 120 for 24 hours. This is what I do when I suspect a bad cooling unit. Doug

[rvman69]

So I guess I should be able to determine fairly quickly if the unit is at least circulating. All of the circulating coils should start warming up. Is this correct? If the circulating coils do not start getting warm after a while then it would mean that either the stuff inside has leaked out or there is a clog in the system. If that is the case there would be no reason to leave it on 24 hours. Is my assumptions correct? I guess then it would be time to order a cooling unit. I hope I dont have to but you have to have a fridge.

[dougrainer]

rvman69 wrote:
Ok so I just hook the two leads from the heating element to an extension cord. Does it matter how the leads are hooked up polarity wise? Do I leave the refrigerator off or does it need to be turned on? I will test the baffle with a stiff wire and see if I can get anything out of it and if it rattles. Then I will blow it out with air compressor. Then I will hook it up to extension cord. I will wait until in the morning so I can be around it for several hours after I hook it up. Is there anything I need to really watch for while it is hooked up. Thanks

Polarity does NOT matter. You do NOT have to be around for the 24 hours. Use a cup of water in the lower section and take the temp from the water. Wiring direct bypasses ALL refer controls. Refer can be off or no 12 volt power to it. Doug