My 3 year old Dometic RM2551 (5 Cubic foot model) isn't cooling well enough on propane. Unable to test in AC. Creeps up to 50f inside ...90F outside. Running an internal and external DC fan. Cleaned the orifice and burner tube. Flame looks great and the camper is level. Side vent and roof vent clear. When I turned it on the first day after 5 months of storage it was 32F inside for 24 hours. Then it started slipping to 50F. Ohm checked the thermistor and it passed. I am stumped. Picture of the flame. https://1drv.ms/u/s!AoCNkn5aOOMYwyGUMDKRnORL7Tu6

The flame looks good...Blue and reaching just up into the bottom of flue center. Need to check thermistor/temp controls by unplugging thermistor from lower circuit board and let fridge run for 12 hrs.Fridge should run continuously and dang near freeze items in food compartmentThermistor leads plug into P2 2 pin connector on left upper areaIf fridge cools down with thermistor unplugged then replace thermistor(even though it Ohm OK)IF fridge does not cool down then you have a ventilation, airflow/draft or bad cooling unit problemWhat FIN do you have thermistor on and where on fin is it?

Any yellow or green powder on the coils?

2oldman wrote:Any yellow or green powder on the coils?That is a great idea. I read about the limp mode when the thermomister is unplugged. I will do that !The tubing that runs up the fridge backside is black with dust. I used my temp gun and get 0F to -4F in the freezer. What is normal for the freezer ? Temp gun shows around 50F on the fins in the fridge. The thermomister is on the furthest right fin middle of the fin. The clamp makes it difficult to put on any other fin.

Wankel7 wrote:The tubing that runs up the fridge backside is black with dust.There shouldn't be any dust on the coils, except maybe for plain old road dirt. Post a picture.

i had a similar problem with my fridge. Turns out the baffle in the flue had rusted and wasn't transferring the heat properly.If Limp mode doesn't fix the problem (or even if it does) check the baffle in the flue (you have to pull it out from the top of the fridge).

Underperforming Dometic Fridge... | Good Sam Community

Wankel7
Explorer
May 29, 2018
Old-Biscuit wrote:
When overheated (lack of airflow/ventilation, interruption of gravity flow etc) the sodium chromate crystallizes and plates out on the inside of tubes.
The crystals accumulate....causing more interruption of gravity flow....more overheating...more crystals

And they are permanent

I agree....

It is going in the trash....picking up a DC compressor fridge tomorrow :)

https://www.coastalclimatecontrol.com/index.php/refrigeration/vitrifrigo.html#!/Vitrifrigo-C115-under-counter-Fridge-w-freezer-Black/p/95699165
Wankel7
Explorer
May 28, 2018
doxiemom11 wrote:
We were having the same problem with our frig - 90 and that side of the rv was in the sun in the morning. Added the dc exterior fan AND finally pulled out main awning out (has been windy) and no more problem.

When you say same issue you had a freezer that was very cold and fridge that was warm?

I have both an internal and external fan.
Chris_Bryant
Explorer II
May 28, 2018
You cannot diagnose a cooling unit problem running on lp, there are too many variables. Everything else will run happily on a 9.5" wc pressure. Test it on 120 volt power, check the lp pressure at the burner.
doxiemom11
Explorer II
May 28, 2018
We were having the same problem with our frig - 90 and that side of the rv was in the sun in the morning. Added the dc exterior fan AND finally pulled out main awning out (has been windy) and no more problem.
Old-Biscuit
Explorer III
May 28, 2018
When overheated (lack of airflow/ventilation, interruption of gravity flow etc) the sodium chromate crystallizes and plates out on the inside of tubes.
The crystals accumulate....causing more interruption of gravity flow....more overheating...more crystals

And they are permanent
Wankel7
Explorer
May 28, 2018
Old-Biscuit wrote:
Wankel7 wrote:
2oldman wrote:
Any yellow or green powder on the coils?

That is a great idea. I read about the limp mode when the thermomister is unplugged. I will do that !

The tubing that runs up the fridge backside is black with dust.

I used my temp gun and get 0F to -4F in the freezer. What is normal for the freezer ? Temp gun shows around 50F on the fins in the fridge.

The thermomister is on the furthest right fin middle of the fin. The clamp makes it difficult to put on any other fin.

Temp guns are not the best method to measure fridge temps with but 0*F/-4*F is perfect temps for freezer

50*F on food compartment fins is NOT good.....cooling unit has blockage between freezer and food compartment
With that cold of freezer temps food compartment should be 38*F

Have you been running fridge 'off level'?????

Force cool it with thermistor unplugged BUT doubt if you will see improvement in food compartment temps
Fin temps should be 10*F lower then food compartment temps measured with a bulb thermometer in glass of water sitting on shelf

Good point. Something is stopping the fridge fins from getting cooled.

The trailer sat nose up all winter. It was cold at times. -15F. I leveled it for two weeks then fired up the fridge while level.

Is a blockage like a blood clot? If it passes it will get caught again?
nineoaks2004
Explorer
May 28, 2018
check the LP system with a manometer, you should get 11" water column, from the last place on the line, if not then you can adjust the regulator so you get the 11". This just happened to me and the problem is corrected.
Thunder_Mountai
Explorer II
May 27, 2018
If you can't find an easy/cheap fix, I suggest you think about a residential refrigerator unless you dry camp extensively. When our evaporation frig in our old MH started doing what you describe, we yanked it out. It was cheaper to go with the residential than trying to repair the old one.
Old-Biscuit
Explorer III
May 27, 2018
Wankel7 wrote:
2oldman wrote:
Any yellow or green powder on the coils?

That is a great idea. I read about the limp mode when the thermomister is unplugged. I will do that !

The tubing that runs up the fridge backside is black with dust.

I used my temp gun and get 0F to -4F in the freezer. What is normal for the freezer ? Temp gun shows around 50F on the fins in the fridge.

The thermomister is on the furthest right fin middle of the fin. The clamp makes it difficult to put on any other fin.

Temp guns are not the best method to measure fridge temps with but 0*F/-4*F is perfect temps for freezer

50*F on food compartment fins is NOT good.....cooling unit has blockage between freezer and food compartment
With that cold of freezer temps food compartment should be 38*F

Have you been running fridge 'off level'?????

Force cool it with thermistor unplugged BUT doubt if you will see improvement in food compartment temps
Fin temps should be 10*F lower then food compartment temps measured with a bulb thermometer in glass of water sitting on shelf
jodeb720
Explorer
May 27, 2018
i had a similar problem with my fridge. Turns out the baffle in the flue had rusted and wasn't transferring the heat properly.

If Limp mode doesn't fix the problem (or even if it does) check the baffle in the flue (you have to pull it out from the top of the fridge).

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