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Old 06-28-2023, 04:23 PM   #1
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Angry Fridge cools on 120AC, but not propane or 12V

Hi All,

I have a a strange issue with my fridge (Dometic RMD8555), it cools completely fine when plugged in on AC power and but will not cool the fridge on propane (which is strange because the freezer works fine on propane).

Same is the case on 12V (freezer works, but not the fridge).

RV tech says he can't find anything wrong with the unit, apart from the fact that the fan behind the fridge won't come on when running on propane.

Anyone have suggestions for how to troubleshoot this?
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Old 06-28-2023, 04:34 PM   #2
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1. You need to fill out your profile with what coach the fridge is in - either that or tell the group what the fridge is in as it makes a difference.

2. If the fridge is in a slide, it very well might not be installed right (and possibly not installed right even if not in a slide).
Ventilation is crucial to LP fridges.

3. LP fridges cool from the freezer down, and their temperatures don’t fall at an even or “tracking” rate. The freezer has to get close to freezing before you begin to notice any appreciable cooling on the fridge section.

4. Not sure on your unit, but if there is a sliding thermistor mounted to the right hand 1-3 fins of the fridge evaporator, make sure the plastic holder is flush with the bottom of the fin it’s on.
Nothing in the refrigerant system modulates the refrigerant flow - the thermistor just tells the control to run until it see’s the preprogrammed temperature setting.
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Old 06-30-2023, 11:22 PM   #3
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The burner can get plugged. Remove orifice soak in alchahol only blow it out with your mouth. Don't use compressed air or spray cans don't poke anything through there it's jeweled has like a little glass bead that can be damaged. You can blow out burner mix tube with tiny bottle brush or several pipe cleaners. One owner had wrong burner tube installed by PO. Make sure spiral diverter is in burner chimney some are built in others dangle on a heavy wire from the top.
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Old 07-01-2023, 08:16 AM   #4
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The burner can get plugged. Remove orifice soak in alchahol only blow it out with your mouth. Don't use compressed air or spray cans don't poke anything through there it's jeweled has like a little glass bead that can be damaged. You can blow out burner mix tube with tiny bottle brush or several pipe cleaners. One owner had wrong burner tube installed by PO. Make sure spiral diverter is in burner chimney some are built in others dangle on a heavy wire from the top.
Thanks, I'll try this. Does this also explain why it's not working on 12V?
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Old 07-01-2023, 08:33 AM   #5
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Fridge has to have 12 volts to operate, regardless of fuel source.

Does your fridge have a 12vdc heater? Makes no sense to have one unless you don’t have LP on the coach (12vdc heater takes a lot of battery to drive a fridge).
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Old 07-01-2023, 09:23 AM   #6
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3. LP fridges cool from the freezer down, and their temperatures don’t fall at an even or “tracking” rate. The freezer has to get close to freezing before you begin to notice any appreciable cooling on the fridge section.

^ this makes the most sense to me.

Even on 12v you're cooling in the freezer per your subsequent post. So, the salient point here is the freezer is cooling but it's not working its way to the fridge. The question, and most possibly the answer, is how your unit draws the cold to the fridge section.
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Old 07-01-2023, 09:22 PM   #7
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Quote:
Originally Posted by SmilingNomad View Post
Hi All,

I have a a strange issue with my fridge (Dometic RMD8555), it cools completely fine when plugged in on AC power and but will not cool the fridge on propane (which is strange because the freezer works fine on propane).

Same is the case on 12V (freezer works, but not the fridge).

RV tech says he can't find anything wrong with the unit, apart from the fact that the fan behind the fridge won't come on when running on propane.

Anyone have suggestions for how to troubleshoot this?
"fan not running on propane" is likely the problem. An absorption cooling unit is designed to cool the freezer first, then as the refrigerant falls(gravity flow) it cools the refrigerator section-IF the refrigerant is losing heat fast enough.
Place a small blower-type fan near the bottom blowing up on the refrigerant piping and observe results.
https://www.newegg.com/p/1YF-00B0-00...9694-_-Product
I have one on my refrigerator and it cools great, in fact I had to reduce the fridge setting to prevent milk from freezing .
I bought my fan when I bought a Fridge Defend protective unit; which protects the cooling unit from damage when the fridge is not level.
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Old 07-01-2023, 10:33 PM   #8
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Dometic RMD8555........

This is a fancy absorption fridge so cooling unit functions the same as any absorption fridge
*fancy in that it uses a software controller & dual gas valve assembly

When 'sufficient' heat is generated enough ammonia is boiled into a hot vapor which is then cooled enough to condense into a liquid
When his liquid contacts the hydrogen gas it absorbs heat from freezer section First and then absorbs heat from food compartment
If the liquid ammonia via condenser is inadequate there will not be enough absorption capability left after going through freezer to properly cool food compartment
**Freezer temp at 10*F then food compartment can cool

IF inadequate..........heat source lacking, transfer of heat lacking or ventilation obstructed
Cooling unit functions properly on 120AC heat source so that is not the issue

Freezer cold/food compartment not on Gas or 12VDC
Low LP System Pressure
Dirty Burner
Dirty flue/flue baffle
Low 12VDC Voltage
12VDC heater resistance low

Exterior Fan is probably NOT coming on when on propane due to lack of sufficient heat being generated so temp at condenser is not closing the t-stat for fan (same for 12VDC heater)
**does it run when on 120VAC heat source???
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Old 07-02-2023, 06:34 AM   #9
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Dometic not cooling on LP

Quote:
Originally Posted by SmilingNomad View Post
Hi All,

I have a a strange issue with my fridge (Dometic RMD8555), it cools completely fine when plugged in on AC power and but will not cool the fridge on propane (which is strange because the freezer works fine on propane).

Same is the case on 12V (freezer works, but not the fridge).

RV tech says he can't find anything wrong with the unit, apart from the fact that the fan behind the fridge won't come on when running on propane.

Anyone have suggestions for how to troubleshoot this?
Let's return the smile to the Nomad,

the reason the fans are not running is that the fridge is not getting enough heat to run the process, in turn not enough refrigerant is being produced. This overheats the boiler while the rest of the cooling unit runs at lower than normal temperatures. The refrigerant is the only thing that keeps the boiler running at its normal temperature without preventive measures.

See these videos, these are for a Norcold fridge, but the principles are the same:

5 LP System Pressure & Filter:



6 LP Gas Burner Igniter Jet & Flue:



Let us know if we can be of further help, Paul and Mao
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Old 07-03-2023, 12:20 PM   #10
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One owner changed LP REG for other reasons, had 9 vs 11 inches water, said Refrig suddenly worked better than ever.
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Old 07-09-2023, 07:04 AM   #11
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It also helps quite a bit to have a small battery operated fan inside near the bottom moving air around. I also have one mounted on the backside of the fridge that assist in keeping air moving upward out the roof vent.

Fans I have...https://www.amazon.com/Fridge-Fan-Co...zcF9hdGY&psc=1
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Old 07-18-2023, 10:23 PM   #12
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This video may help.


I would check the relay mentioned. Mine was bad, so fans would never start. Easy to check/replace without removing refrigerator.

Since I fixed the rear fans and installed a fan on the inside of the fridge pointing at the fins, mine stays at 34 to 36 degrees.
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