Dometic RM2351 refrigerator propane issues

[TWX]

I've had a problem with the Dometic RM2351 under-counter refrigerator in my 2019 Jayco 174BH. Back in the summer we went out of the Phoenix area into the high country on the hottest day of the year and it wouldn't stay running on propane. Fast forward and the problem persists into the winter time. The symptom is that when trying to operate on gas it starts the flow, it ignites the gas and I can hear it burning, but when it turns off the igniter it also turns off the gas flow. After a couple of cycles of this the "check" light illuminates and it no longer attempts to operate on propane. It does this whether or not the fridge starts out cold or starts out ambient temp.



Back when the problem initially manifested both the cooktop and the water heater worked. Testing this time around I just lit the cooktop, it works. I constructed my own manometer:

and I measured at three places. First place, I had installed a fitting on the manifold to allow for hooking up an external fire pit. On my homebrew tool I got 15" WC. This is technically a little higher than the 11" WC specification, but is less than the 22" WC max pressure on the sticker on the back side of the fridge for testing purposes.


Second place, I measured at the jet, I got 13" WC while the fridge was enabled and attempting to light.


Third place, I measured past the valve with the jet removed, and likewise got 13" WC while the fridge was trying to light.


While I had everything apart I reassembled the solenoid housing into the burner housing, reinstalled the jet, and confirmed that the igniter was within spec distance to the burner emitter, then without installing back onto the fridge housing had my wife turn the fridge on. The burner successfully lit and I could see visible flame and feel heat from it.


Resassembling into the trailer on the back of the fridge, I confirmed that it would light (and I could hear the gas burning) but it would shut off the solenoid when it was done cycling the igniter, even when the door was open so it was warming up enough to have a reason to run.


At this point I'm running out of ideas, any suggestions would be much appreciated

 

[TWX]

I should add, there's no thermocouple connector on the fridge PCB, and I don't see a thermocouple...

The behavior exhibited is like the thermocouple is bad and not sending a sense back to the PCB that the fridge is lit, but the part is physically not part of the fridge in the first place as far as I can tell.

 

[TWX]

Did some more digging, it appears that somehow it uses the igniter as a flame sensor, not sure how that affects troubleshooting. It's supposed to detect flame and then shut off the ignition system immediately. This unit keeps running the igniter even after it has started making flames.

 

[craigav]

You are correct that the ignitor is the flame sensor and commonly needs to be replaced whenever the issues you reported are occurring. It is hard to test them as the current and volts of the sensor are very low. Less common is the control board failure.

I would likely pull down a troubleshooting chart or simply replace the ignitor/flame sensor. Also, if somehow the tip of the ignitor is not bright and shiny, I would clean it up first as a test using steel wool or sandpaper. ~CA

 

[TWX]

You are correct that the ignitor is the flame sensor and commonly needs to be replaced whenever the issues you reported are occurring. It is hard to test them as the current and volts of the sensor are very low. Less common is the control board failure.

I would likely pull down a troubleshooting chart or simply replace the ignitor/flame sensor. Also, if somehow the tip of the ignitor is not bright and shiny, I would clean it up first as a test using steel wool or sandpaper. ~CA

Supposedly an honest-to-goodness Dometic replacement board was on Amazon, I have it on order to receive tomorrow. The igniter is well within the flame and I spent time trying to make adjustments to see if I could get it to work, no dice.

The angle in this photo was fac'try:

 

[TWX]

I appear to have lucked out. The new part arrived from Amazon several hours earlier than expected, so I had time to change it out right as it was transitioning from dusk to proper nighttime. It does seem to be a genuine Dometic part too, not some DWLHXP or other fake brand of random letters as a knockoff:

I verified that the battery was turned off and I unplugged the trailer from electrical service before proceeding with the swap. As I pulled the individual terminal-lug wires off of the old unit I wrote what they were, either a letter or the terminal position number (ie J2,J4, etc) just to keep everything straight.

Old one (bottom) and new one (top) for comparison:

The new one is a lot smaller but the outer mounting tabs are in the same places and the connectors along the bottom edge are in the same order too. They did away with the grounding screw on the bottom right corner, one must ground using the terminal lug. Mine already used the terminal lug so this doesn't seem to matter as much.


New one in and connected:

Obviously power was still off while doing this. The wires were tight, the connectors were not in the exact same position board to board, so I did have to fight with them a little. The bigger fight was the retaining screw on the left side, the opening to the back of the fridge isn't large enough and is positioned too far to the right so it was difficult to get to that screw. It would be an awkward job to do on the road without a stubby #2 Philips screwdriver.


Once it was back together I turned on battery power and successfully lit the burner. At this point it was well and truly nighttime so I was able to see the glow of the burning flame once the ignition cycling stopped as it detected the flame:

After it ran on propane for a bit I plugged the trailer back in to 120VAC power and switched the fridge from gas to auto, I could hear the solenoid shutting off the gas flow.


I left it on auto (electric) for overnight testing, want to confirm that the fridge is properly running on electrical power. Will check in the morning.


So the replacement board for the RM2351 is 3316348.900. The cover has p/n 3316348.000 on it. It was around $70 shipped from Amazon. I wonder if it was so much cheaper than I saw other Dometic boards for because they realized they screwed up with the design and lowered costs to make repairing easier than getting tons of negative reviews.


For the future as a precaution, if I run my trailer off of my small generator, I'm going to shut off the 120VAC breaker to the fridge and leave it on propane. I cannot say if testing running the rooftop AC on the generator without ensuring that the fridge wasn't on 120VAC is what caused the failure or not, but I cannot rule it out. Since the Baja Edition comes with the larger propane tank I don't need to run the fridge on generator power, I may as well avoid it to hopefully avoid weird electrical loads on the appliance.

 

[TowPro]

This refreg should be able to stay on propane even if 120v is supplied to it if the switches are set correctly. I used to leave mine turned on running on propain all summer. It emptied a 20lb tank in about 50 days. https://www.gas-refrigerators.com/p...kLDBdXkBYFQbB80h9pOhZPrQ4OM1oiDT42WV-Sc9lCyL6

 

[TWX]

This refreg should be able to stay on propane even if 120v is supplied to it if the switches are set correctly. I used to leave mine turned on running on propain all summer. It emptied a 20lb tank in about 50 days. https://www.gas-refrigerators.com/p...kLDBdXkBYFQbB80h9pOhZPrQ4OM1oiDT42WV-Sc9lCyL6

If I have it set ON and GAS it will do that, but I'd rather it be able to run on 120V AC when I'm able to plug in.


After it was able to successfully start on propane I ran it overnight on electricity, and it did cool down successfully. I then ran it on propane for an extended period of time and it worked fine, and have now run it for electricity for a couple of days and it seems to be doing well.


It would be nice to have a three-way unit that could run off of 12V batteries, but this trailer is so lightweight that this really isn't a practical solution unless I'm reworking the whole electrical system. And this trailer simply isn't built well enough from the factory to be justified in putting that kind of work into it.

 

[bjferg]

Sounds like a similar issue we had. Thought it was the thermocouple but it ended up being the thermostat was done. I replaced selector switch, thermocouple and finally fix issue when the thermostat was replaced.

 

[TWX]

Sounds like a similar issue we had. Thought it was the thermocouple but it ended up being the thermostat was done. I replaced selector switch, thermocouple and finally fix issue when the thermostat was replaced.

I'm not sure how this is similar?


The circuit on the PCB that interprets the change of state of the thermocouple based on being bathed in flame had stopped working, so it was sitting there continuing to spark the igniter even when the flame was going.


This required replacing the board itself. No switch in the human-operated sense or thermostat in the interior temperature or the chimney stack sense.