Dometic RM1350 refrigerator not working

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TomnDine

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Jul 8, 2019
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Good morning
I am out on a month long trip and our refrigerator has stopped working, Dometic RM1350.  I have downloaded the service manual and gone thru the troubleshooting steps and believe the cooling unit may be dead, but have a couple unanswered questions?

The boiler gets hot on BOTH propane and electric but the coils no longer heat up. 
Can the control board cause this?  or does the control board ONLY control the boiler operation?

There is no apparent leak in the cooling unit, no odor whatsoever ( I have had one go out on another rv and it clearly smelled of ammonia).

The thermistor checks out as it should with an ohmeter both in icewater (9100 ohm) and ambient (5000 ohms)

all control buttons and digital display working properly

Unit is 2009 and has always maintained 34 f tremp.  Problem started out as intermittent, would stay at 34 f  for days then spike to upper fortys and fiftys and then cool back down to 34 for a couple days and then spike again and eventually stopped cooling altogether even though boiler gets hot

This just seems like a control issue rather than the cooling unit and I would hate to replace the cooling unit only to find out it still doesn't work

Any help or insight would be greatly appreciated, please feel free to email me as well as post a reply.  Right now we are using a small (very small) electric fridge for basics.
 

regval

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Jun 4, 2015
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Lawrenceville, Georgia, USA
The boiler is the long vertical tube immediately above the LP burner and the temperature should be quite high, above 350 degrees during operation. The absorber vessel is located at the left or central part of the cooling unit at the very bottom and is shaped like a tank. When operating, the absorber vessel and the metal coils immediately above the absorber vessel should be warm to the touch, not hot, but warmer than ambient temperature.
The control board either turns on the gas burner or the electrical heating element to heat the refrigerant liquid, so if the LP burner ignites, the control board is responding to the thermistor's call for action.
If you have no cooling in the freezer compartment, no evidence of ammonia leaking, the absorber coils are cool and the boiler is hot, then I think your cooling unit has failed, possibly due to an internal blockage.
 

Gary RV_Wizard

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West Palm Beach, FL
Agree with regval.  The controller can only turn on the boiler heat in response to the thermister temperature signal.  Once it does that, it merely waits until the thermister reports an ok temp. It has no control over how the cooling unit performs.

You won't necessarily see yellow powder or smell ammonia when the cooling unit fails.  In fact, the first phase of failure is often a pinhole leak in which the hydrogen gas component of the coolant leaks out, and hydrogen is odorless and colorless.  Once the hydrogen is lost, 2nd stage cooling (the fridge section) pretty much stops dead. The freezer may still have some cooling.

If the tubes running from the condensor at the top back down to the reservoir & boiler at the bottom do not get moderately warm to the touch, the cooling unit isn't working.
 

JD Sharp

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Jun 20, 2009
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234
Location
Ferndale, WA
This will sound crazy but tap the cooling unit with rubber mallet. Our refer failed (2004 Beaver Dometic) in Florida Keys when I asked a service man to helps us he said he was too busy to come but tap on all the tubes of the cooling unit. It worked, and kept working till we sold the motorhome.
 

TomnDine

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Jul 8, 2019
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I am now seeing yellow powdery substance covering the burner and temp sensor.  Never smelled any ammonia odor.  Did have a strong garlic smell in freezer but assumed it was actually "garlic" as pretty much everything in our freezer contains garlic :)

So, I assume the "yellow Powder" is a death sentence for the cooling unit?  If so I will order a replacement
"Amish" cooling unit as that is what I did last time and it functioned WAY better than the original Dometic.

Thanks for the help.
 

Gary RV_Wizard

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So, I assume the "yellow Powder" is a death sentence for the cooling unit?  If so I will order a replacement
"Amish" cooling unit as that is what I did last time and it functioned WAY better than the original Dometic.


Yeah, the yellow powder is a death signal. The ammonia has leaked out around the boiler and evaporated, leaving the yellow sodium chromate behind.

So this will be your third cooling unit in 10 years?  That's extreme and indicates it is being operated off-level or exposed to something caustic enough to accelerate rust spots.
 

Wetheking

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Jun 18, 2021
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Temecula, CA
I have a 2019 RM1350 MX. It does not like it when it gets anywhere close to freezing outside. It will go into EO communication error code. Can kill power and 12volt for 20 minutes as many times as you want and it will reset for a minute and then go back into E0. Once it warms up it will reset and run just fine. When it is acting up it doesn't matter weather its on Gas or Electric. It will not reset until it warms up to say 35-40 degrees then it is happy. I am guessing the main circuit power module that is exposed to the cold has a bad solder joint or cracked circuit board? I am going to replace this main power module and see if that fixes it.
 

Kirk

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Oct 30, 2005
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Full-time , Escapee
SECTION 10 Error Codes:
The codes are displayed flashing (alternating between temperature and message) on the display. No communication between display and power modules. The control system will revert to full automatic operation selecting the best energy source available with AC first and GAS being second priority. The temperature setting will be maintained at the mid position. The power module will continually attempt to reestablish operation of the display module. Test control cable between upper and lower control, control (on-off) panel and lower board, clean all grounds, and try a different DC power source. If problem still exists change lower control board.

The above comes from the RM 1350 service manual.
 

Henry J Fate

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Jun 14, 2018
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1,979
I have a 2019 RM1350 MX. It does not like it when it gets anywhere close to freezing outside. It will go into EO communication error code. Can kill power and 12volt for 20 minutes as many times as you want and it will reset for a minute and then go back into E0. Once it warms up it will reset and run just fine. When it is acting up it doesn't matter weather its on Gas or Electric. It will not reset until it warms up to say 35-40 degrees then it is happy. I am guessing the main circuit power module that is exposed to the cold has a bad solder joint or cracked circuit board? I am going to replace this main power module and see if that fixes it.

Sounds like a bad solder or a bad component but could also be a bad connector to the board. I would first re-seat the connectors and check them for any adverse conditions. clean everything. Pull the board and get it under a good light with magnification and have a look. You may be able to find something that looks suspicious or even obvious. Best approach is to re-flow all the solders. You should have access to the bottom of the board but the top side will probably be incased is a protective silicone that is not easily removed.

A good way of testing for the above board problem is to apply some heat to the board with a household hair dryer to see if it rectifies the problem. You could also re-seat the connector on the board to see if that works too.
 
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