Fridge not staying lit on propane

ADK_ Adventures

Active Member
Apr 17, 2021
133
Hello everyone!

I'm having some trouble with our camper fridge, and I would like to ask some questions please. We have a new-to-us 2001 Starcraft popup with a Dometic RM2193 3-way refrigerator that works fine on 120v but it's running sporadically on LP gas, and I'm going nuts trying to figure this thing out. Short story is, I can get it to light no problem, it runs for anywhere from about 3 to 16 hours, then I check it and the flame is out and flu is ice cold. Probably a dumb question, but is this behavior normal? Are these fridges just kind of flakey and you have to keep checking them? If not, what might be causing this?

I know there is a safety device that will shut the gas off if there is no flame. However, if this part was malfunctioning don't you think the fridge would shut off after maybe a minute or two or three? It doesn't make sense to me that it can run for hours and hours, then suddenly shut off. I will note that when it shuts off it does indeed shut the gas valve because I can hear it when it's flowing, and I can hear the difference when it's not. I'm just not sure if the flame is getting blown out somehow and then the gas valve closes (as it should), or if something is causing the gas valve to shut seemingly randomly.

Here's some further details:
I have a recently filled tank of gas.
I have a brand new LP gas regulator installed, 2 stage, 11" wc pressure (ideal for my gas appliances (ie a furnace and a fridge)).
I am bypassing the camper gas lines and connecting my LP tank directly to the gas inlet on the fridge at the service panel.
I have completely disassembled the burner unit and cleaned it of debris, soaked the orifice in isopropanol as described in the manual and no change.
I found the exact same fridge for sale on Craigslist for $25 and got it as a a "parts fridge" (it's much dirtier than mine). I ran this fridge overnight without problem, so I assumed its components were good. I have since swapped out the burner assembly, the ignitor, the sparker coming from the ignitor, and the electrode the spark jumps to (and then goes back the gas valve and I *think* this maybe the sensor that detects if the flame is lit or not). Even after that I still have the same problem; it runs for a few hours, then goes out somehow.

I have not tried to clean the flu, and I have not tried to swap the board with all the switches on it. Could this be the problem? I don't really have an electronic control board, it's just a board with switches and relays, and it looks like a thermistor is coming into it from the cooling fins inside the fridge. Could this thermistor have anything to do with my problem? It doesn't look easy to swap this switch board because of the way the thermistor is attached to it, I think I'd have to figure out how to remove the thermistor as well. I am now wondering if the thermistor might be the problem though. Any thoughts? I really don't want to go pulling this thing further apart if I'm not going in the right direction.

My service manual:
https://www.scamptrailers.com/wp-content/uploads/Dometic_Refrig_RM2191_RM2193.pdf

Thank you for your help!

-Amos
 

geoffm3

Active Member
Jun 21, 2010
180
It sounds like your thermocouple is working if it stays on for more than a few minutes at a time, but they are pretty cheap so you could throw a part at it and see if that addresses it. On our old hybrid camper, I had to replace the burner/orifice assembly because it wouldn't stay lit, and also another time the thermocouple because it would go out as soon as you took your finger off of the plunger. Both parts are typically pretty cheap.

The Dometic fridge in our Palomino is a little sputtery at startup unless you first purge the gas line by lighting the stove inside. I will usually light the inside stove, and then light the fridge... it'll sputter and go out a couple of times, and then will stay lit after all the air is out. I have had it go out after about 15 minutes a couple of times with a first startup, so I will usually let it go for a half hour after lighting and recheck that it stayed lit. Other than that, it's been pretty reliable (knock on wood)
 

ADK_ Adventures

Active Member
Apr 17, 2021
133
Thank you for your reply. I have already replaced the burner assembly as well as a few other components. I’m not sure exactly what the thermocouple is on my fridge, it I think it’s what the electrode spark jumps to at the burner. Maybe someone could clear that up for me. Either way, I have replaced that part too.

I also believe I have a thermistor in the cooling fins inside the fridge, it has a wire that comes out of the back of the fridge and into my switch board. I am wondering if this thermistor is the problem?

Thank you for your help!

-Amos
 

davido

Super Active Member
Jul 17, 2014
1,372
Thermocouple is a little heat sensor that has a braided wire coming out of it and extending into the fuel regulator on the back of the fridge. The way it works is when there is heat (from the flame) the system detects that and keeps the fuel flowing. When there is no heat, the fuel flow is interrupted.

It is thanks to this device that you have to hold the on-off knob in when you're igniting the fridge, and continue to hold it for 15 to 30 seconds after the fridge ignites. Until the heat signal is detected, the fuel would just shut off when you release the on-off knob. Once that heat is detected, you can release the knob and the fuel continues flowing.

So the possible culprits:

  1. Thermocoupler is failing to detect heat or send a signal.
  2. The fuel regulator in the fridge is becoming faulty; it could be failing to recognize the thermocoupler's signal, or it could be clogged.
  3. The burner bowl could be dirty.
  4. The fuel jet could be clogged (mine had a spider crawl inside and make a nest).
  5. The fuel lines running from the main regulator (by the tank) are leaky (very unlikely).
  6. The fuel pressure regulator at the tank is faulty (also unlikely if any other devices work ok).
Oh, and there's also the possibility that it's getting blown out due to a missing peep-hole door. Most of these fridges have a little sliding door near the flame so you can visually see that the flame is burning. If that door is opened or missing, a puff of air could blow out the flame.
 

Anthony Hitchings

Super Active Member
Silver Supporting Member
Mar 2, 2019
3,768
Oakland, California
AFAIK the thermocouple only works for AC (you can see this on the schematic). When using propane the gas valve is "set and forget" unless you want to change the temrpature - its not (!!!) automatic.
 

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geoffm3

Active Member
Jun 21, 2010
180
AFAIK the thermocouple only works for AC (you can see this on the schematic). When using propane the gas valve is "set and forget" unless you want to change the temrpature - its not (!!!) automatic.
Nope, only for gas. It's purpose in life is to shut off the gas supply if it detects that the flame has been put out so that you don't accumulate unburnt LPG in a confined space and blow yourself up.
 

ADK_ Adventures

Active Member
Apr 17, 2021
133
Hey all! Thanks for the replies and advice!

I had honestly tried just about everything that I think was suggested here in this thread including cleaning the burner assembly and orifice, replacing the burner assembly and orifice, replacing the thermocouple, ignitor, and ignitor electrode. I don't even remember everything I've tried so far. Nothing seemed to make any difference, and I kind of still think it may have something to do with the thermistor in the inside of the fridge. Or, that it's just prone to the flame blowing out, even though I have the cover box with the peephole installed.

As mentioned in my first post, I had purchased a 2nd fridge to use for parts. I originally didn't want to simply replace the fridge because I thought the job looked like a lot of work, and because the 2nd fridge was much less clean than my original fridge, especially the door gasket which had a lot of mold on it. But, the 2nd fridge seemed to run well, so I decided to pull out my original fridge after all. Turned out to be pretty easy. I took the best/cleanest parts from each of the refrigerators and put together one "Frankenstein" fridge. I had to remove the door and door trim to get them in and out of the camper door, so I used my original door on the 2nd fridge, and everything cleaned up nicely, it looks like a brand new fridge on the inside. I was also able to paint the fridge door trim to match my camper interior better, so that was a plus.

And now my Frankenstein fridge is reinstalled and has been running on gas flawlessly for a good 8 hours now with no sign of quitting. I think it's even heating the flu hotter than my original fridge did when it was running. I'm going to let it go overnight, and hopefully even a good full day or three to make sure it's really working, but I'm hopeful I got it now.

I do have a question though. When I pulled out the original fridge and got a good look at things I noticed what looked like debris in the input gas flange fitting on my original fridge. It looked like dense spiderwebs, or that cottony looking bug material that looks like cocoon fibers. I saw this blockage in the flange fitting and I thought, that's it, this has to be my problem! I got a pick and picked it out, and instead of being bug material it's clearly some kind of purpose made filter. It's the size and shape of a pencil eraser, and looks like similar material to a cigarette filter. My question is, is this supposed to be there, or did someone shove this in place in error? Could this be what was causing my issue?

Thanks again for your help!

-Amos
 

geoffm3

Active Member
Jun 21, 2010
180
Hey all! Thanks for the replies and advice!

I had honestly tried just about everything that I think was suggested here in this thread including cleaning the burner assembly and orifice, replacing the burner assembly and orifice, replacing the thermocouple, ignitor, and ignitor electrode. I don't even remember everything I've tried so far. Nothing seemed to make any difference, and I kind of still think it may have something to do with the thermistor in the inside of the fridge. Or, that it's just prone to the flame blowing out, even though I have the cover box with the peephole installed.

As mentioned in my first post, I had purchased a 2nd fridge to use for parts. I originally didn't want to simply replace the fridge because I thought the job looked like a lot of work, and because the 2nd fridge was much less clean than my original fridge, especially the door gasket which had a lot of mold on it. But, the 2nd fridge seemed to run well, so I decided to pull out my original fridge after all. Turned out to be pretty easy. I took the best/cleanest parts from each of the refrigerators and put together one "Frankenstein" fridge. I had to remove the door and door trim to get them in and out of the camper door, so I used my original door on the 2nd fridge, and everything cleaned up nicely, it looks like a brand new fridge on the inside. I was also able to paint the fridge door trim to match my camper interior better, so that was a plus.

And now my Frankenstein fridge is reinstalled and has been running on gas flawlessly for a good 8 hours now with no sign of quitting. I think it's even heating the flu hotter than my original fridge did when it was running. I'm going to let it go overnight, and hopefully even a good full day or three to make sure it's really working, but I'm hopeful I got it now.

I do have a question though. When I pulled out the original fridge and got a good look at things I noticed what looked like debris in the input gas flange fitting on my original fridge. It looked like dense spiderwebs, or that cottony looking bug material that looks like cocoon fibers. I saw this blockage in the flange fitting and I thought, that's it, this has to be my problem! I got a pick and picked it out, and instead of being bug material it's clearly some kind of purpose made filter. It's the size and shape of a pencil eraser, and looks like similar material to a cigarette filter. My question is, is this supposed to be there, or did someone shove this in place in error? Could this be what was causing my issue?

Thanks again for your help!

-Amos

Good question. I didn’t notice anything like that on our fridge when I had it out. Does it show up in a parts diagram?
 

ADK_ Adventures

Active Member
Apr 17, 2021
133
Good question. I didn’t notice anything like that on our fridge when I had it out. Does it show up in a parts diagram?
Not that I can see anywhere in the diagrams or manual, that's why I'm questioning this filter.

The Frankenstein fridge has now been running flawlessly for almost a full 24 hours, I don't think my original fridge ever went that long without shutting down. And this morning the little cup of water I left in the fridge was a solid block of ice. At some point I will shut down the Frankenstein fridge and try to look and see if the gas valve on that one has this filter. It's almost impossible to see with the fridge mounted in the camper because you're looking at the profile of the gas valve, not down into it.

I'd really like to know if this filter is supposed to be there or not, or maybe it's just old and needs to be changed?

Thanks for the help!

-Amos
 

ADK_ Adventures

Active Member
Apr 17, 2021
133
Alright, I just did a little more searching, and on the full parts diagram available here, there is definitely supposed to be a filter in place. I guess it's possible mine is dirty, but it's definitely supposed to be there.

-Amos
 

geoffm3

Active Member
Jun 21, 2010
180
Alright, I just did a little more searching, and on the full parts diagram available here, there is definitely supposed to be a filter in place. I guess it's possible mine is dirty, but it's definitely supposed to be there.

-Amos
Hmm... that's the same model fridge as ours. I didn't notice a filter but I wasn't really looking down in the inlet fitting when I had it out either. :)
 

ADK_ Adventures

Active Member
Apr 17, 2021
133
Hmm... that's the same model fridge as ours. I didn't notice a filter but I wasn't really looking down in the inlet fitting when I had it out either. :)
Yep, it’s supposed to be there, but maybe really hard to see it. If you click the link in my last post and look at the diagram for the control parts and it’s part #43.

On the plus side, my repaired fridge had been running flawlessly for 48 hours now, so I’m pretty happy about that.

-Amos
 




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