Dometic RM2351 Refrigerator not lighting with gas

[Christy_T_]

We have recently purchased a used travel trailer with a Dometic fridge that probably hasn't been lit with gas for quite a long time. Works fine on electric, but when we try to switch to gas, it won't stay lit. We purged air from the lines and have done a rudimentary cleaning of the flue baffle and burner. The spark-lighter successfully ignites a flame over the burner tube, which is clear blue over the slots, but as soon as the igniter stops, the flame goes right out. We have turned it off and on and tried multiple times with the same results. Can anyone suggest what might be the problem?

[Christy_T_]

Hooray! At last, we have a cold refrigerator working off of gas! We just ordered a flame sensor and a control board and put them both in and now it's working fine. Don't know which one was actually bad, but they're both good now. Thank you all for the advice and support. It was greatly appreciated!

[j-d]

Flame Sensor Theory of Operation link I mentioned. The sites I searched emphasized they are info and discussion not DIY. Their theme is "If you are not a professional, call one."

[j-d]

I looked at manual above and it mentions only Thermocouple, which is the Two-Wire device pictured above. Diagrams in the above manual show a Two-Wire device, which is a Thermocouple. If Christy found a single-wire sensor, it doesn't seem to be covered in the manual. I looked up how a Flame Sensor works and it's pretty involved. Different ionization rates because the Burner Surface and the Flame Sensor have significantly different surface areas. The flame therefore causes an uneven flow of AC current. Blah Blah Blah. Testing sounds tricky. I think what I'd do is clean the Sensor, its Connection, the top of the Burner, and the joint were the Burner grounds to the rest of the Fridge. I can link the article I found if you like.

[hhornig]

Here is the service manual for your unit. It appears that you need to measure resistance between the electrode and ground.

http://www.nancyemmert.com/region6/Resources/NewDometicRefrigeratorManual.pdf

[hhornig]

Here is the service manual for your unit. It appears that you need to measure resistance between the electrode and ground.

http://www.nancyemmert.com/region6/Resources/NewDometicRefrigeratorManual.pdf

[hhornig]

I am not familiar with that sensor, but you would normally connect the red lead of the multimeter to the wire and the black lead to the piece that attaches it to the frame (ground). I will see if I can find what reading you should get. I would not leave it attached to the control panel while heating it in a flame.

[Christy_T_]

We definitely have a "one-wire" flame sensor. I'm not clear on how this process of checking it with the multimeter looks. Its' connection at the control panel looked clean and good. So, I leave it connected to the control panel, hold its' tip in a gas flame (generated by what?), then I don't know where to place the leads from the meter. Thanks for your patience. This is new territory for me!

[j-d]

Just found pix of both the Sensor and the TC on Amazon.
Flame Sensor:
Porcelain Insulator, ONE Wire Connector
Thermocouple:
Made of Brass with a few inches of Copper Tubing, then TWO Single-Wire Connectors
Again, which do you have?

[j-d]

The Meter's Test Leads are the two coiled wires in the photo. Red to POS, Black to COM. Third socket in meter not usually used. The "Leads" on the Spark Electrode would be the wires that connect the device to the rest of the fridge, at whatever part that happens to be.
Did you figure out if you have a Flame Sensor or a Thermocouple? OB, above, is rarely wrong. His post says your fridge Serial Number will tell you which device you have.

[Christy_T_]

Trying to test the spark electrode with the multimeter. Can anyone tell me what the "leads" are?

[j-d]

Don't hold me to it, but at least on an older Dometic fridge I replaced the Thermocouple on, it connected at the Gas Valve, not at the Control Board. A Flame Sensor, I believe, would connect at the Control Board. The test described above, holding the TC tip in a flame and measuring the millivolt output, would call for a meter. Doesn't have to be expensive. The one pictured here from Harbor Freight is $3.99 on sale, and often free on a coupon with another purchase.

Hardware stores, and probably Lowe's/Home Depot, have generic TC's. So long as you can make the connection and mount the tip into the flame, a generic will work.

[Christy_T_]

Thank you all for your suggestions. We won't be able to try these ideas until the weekend now, but I'm looking forward to trying to diagnose this. We generally only camp where there are no hook-ups, so we need the fridge to work! Thanks again.

[hhornig]

Chances are that your thermocouple or your circuit board is bad. Remove the thermocouple and hold the tip in a gas flame with a multimeter across the leads set to the millivolt range. The voltage should be somewhere in the 20-30 mv range. If it is the circuit board is bad. If not in the range your thermocouple is bsf.

[Old-Biscuit]

Depending on model year (serial numbers) the Dometic RM2351 used a 'thermocouple' and later model year uses a spark electrode (which is the flame sensor).


Your main flame is lighting off (good spark) but won't stay lite because circuit board is not getting the flame proof signal....either bad sensor (likely) or bad circuit on board

Dometic thermocouple....part #2932052018.......LINK


Dometic spark electrode....part #2932781012.....LINK


Before replacing....pull thermocouple/spark electrode (whichever one you have) clean the connection at board...make sure it's tight and clean up thermocouple. Spark electrode gap should be 1/8" and both need to be engulfed in main flame.