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Old 05-15-2021, 05:43 PM   #1
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Dometic frig not cooling.

My 10 year old Dometic AC/ Propane frig has lost most of its cooling ability. I have viewed several YouTube videos and have exhausted all of my troubleshooting ideas. Everything checks out, yet it's not cooling. It's almost like the ammonia has just evaporated overnight. Any thoughts?
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Old 05-15-2021, 08:19 PM   #2
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Quote:
Originally Posted by vetplus40 View Post
My 10 year old Dometic AC/ Propane frig has lost most of its cooling ability. I have viewed several YouTube videos and have exhausted all of my troubleshooting ideas. Everything checks out, yet it's not cooling. It's almost like the ammonia has just evaporated overnight. Any thoughts?
Usually when they spring a leak, you do loose most of the charge in a very short period of time. Can you see any evidence of a leak. When they do spring a leak they leave behind residue, and you can usually smell them.

If that's the case the only solution is to buy a new cooling unit. Lots cheaper than buying a new fridg.

I can assume when you turn it on propane you can hear and see a flame? And on AC you have put a load meter on the AC line to verify it is drawing power?
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Old 05-15-2021, 10:37 PM   #3
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Everything checks out, yet it's not cooling. It's almost like the ammonia has just evaporated overnight.

What is EVERYTHING??

What troubleshooting have you done?

*Ventilation
*Airflow/Draft
*Level when operated
*Same non-cooling on AC and Gas
*Running w/o thermistor
*Force Cooling
ETC???



Ammonia doesn't evaporate insides a sealed/pressurized vessel....cooling unit is under 300PSI
Leak allows ammonia and the hydrogen gas to escape
Sometimes a yellowish residue is present ....that is the sodium chromate that leaked out and dried (anti-rust inhibitor in the coolant solution)
**If present...it is toxic so do not blow it out using aor pressure...best to vacuum up (mask/glove...wash afterwards)

MODEL would be helpful
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Old 05-16-2021, 05:03 AM   #4
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Model # DM 2652 RBFX

The heating component works on both AC and DC. I can see the propane flame and I put an amp clamp on the heater wires to verify the AC side. The two air flow fans work as well.
When I unplug the AC, the freon ignites and heats the boiler. When I plug the ac back in, the relay on the control board closes and sends AC to the heater at the boiler.

There is no ventilation issue that I can see and the rv is level. My unit hasnt been moved in two years and the fridge has never missed a beat. I have two fans that are moving air across the coil.

The coils are hot on the back side of the freezer side (as I have partial freezer cooling) but the coils are at ambient temperature on the back of the refrigerator side. I am wondering if I simply have a sediment plug that has impeded gas flow.

I have checked the unit for signs of a leak and found none. In addition, I have never smelled any ammonia smell.
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Old 05-16-2021, 09:08 AM   #5
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Maybe the thermistor ( temperature sensor ) that is mounted on the fins has gone bad or gotten unplugged?
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Old 05-16-2021, 09:59 AM   #6
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OK....
So the AC Element does get energized
And fridge swaps to GAS when there is no AC and the GAS ignites
Fans working
No Ventilation Issues
Fridge operated level


SO now you need to do some more troubleshooting
*Door seals........warm air leaking in displaces the cold air...fridge doesn't stay cold

*Unplug thermistor leads at lower control board (2 white leads...left side) Run fridge for 12 hrs on AC power and check results
Fridge gets cold...replace thermistor
Fridge does NOT then need to force cool

**Force Cool
Unplug the AC element Leads from control board
Plug then directly into the 120VAC Outlet energizing the element continuously (Bypasses ALL controls---force cooling the fridge)
Run fridge for 12hrs and check results
If fridge gets cold.........replace lower circuit board
If fridge does NOT get cold.....bad cooling unit
***Force cooling is last step in troubleshooting
IF cooling unit is capable of cooling it will when 'force cooling' is done
If cooling unit has an internal obstruction/blockage force cooling will verify it is bad unit


Internal obstructions occur from overheating of coolant...sodium chromate crystalizes and plates out on inside of coils/tubing.
Causes more obstructions...more overheating....more crystals etc etc
Process is accumulative and permananet


Symptoms of bad cooling unit
*lack of cooling on either heat source
*Ammonia smell....yellowish residue
*Partial cooling of freezer but no cooling in food compartment



From your description....obstructed/blockage between freezer coil and food compartment coil
But finish the troubleshooting and verify WHY the lack of cooling
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Old 05-17-2021, 04:23 AM   #7
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The thermistor checks good.
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Old 05-17-2021, 04:31 AM   #8
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The thermistor checks fine. I live in this unit on the road, so troubleshooting time is a luxury that I dont have.

The boiler is staying on due to the thermistor working properly and the fridge being at ambient temp. As such, that essentially seems to be the same as "forced cooling". The board is calling for heat to cool the fridge.
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Old 05-17-2021, 11:20 AM   #9
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Then if you do not have time?? to troubleshoot
Bad Cooling Unit....need time to replace it
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Old 05-17-2021, 01:20 PM   #10
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I am moderately handy, but knew nothing about RV refrigerators before I found myself in a similar situation as yours. I did the trouble shooting and determined that my cooling unit was bad. A local shop wanted to put in a brand new refrigerator for ~$2500. (My RV was only 5 years old, but was an ex-Rental so had 120k miles on it...lots of use). I decided to replace the cooling unit myself to save $$$. It cost ~$750. I was surprised that the total job only took me 4-5 hours by myself. Refrigerator has been working GREAT ever since.


Plenty of youtube videos on the process. Got my cooling unit from rvcoolingunit.com and they were VERY helpful.


Good luck!
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Old 05-18-2021, 05:03 AM   #11
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I went ahead and replaced mine with a larger residential unit. I never used the propane option on the old one anyway.
Just out of curiosity, was your cooling unit a returned one?

Thanks to all that replied.
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