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Old 07-20-2021, 10:18 PM   #1
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Dometic Absorption Refrigerator only working on DC battery, not on gas or AC power

Hello, I have a small Dometic Absorption Refrigerator (model RM 4223) that has started working only on DC battery, not on gas or AC power. This is a refrigerator only unit. It will get very cold (below freezing around 30 degrees) on battery DC power, while the AC and Gas might get it to down 45 degrees when it's cool outside at night. During the high heat of day (around 100) the battery will maintain appropriate temp, but the AC and Gas won't keep it under 75 degrees F.


Some things I've checked: it is level. It also has AC power...no blown fuses or breakers. Gas is on and pilot and burner are operating correctly.


Any ideas?
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Old 07-21-2021, 11:27 AM   #2
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Have you looked at the manual?

It says “ In the case of the RM4223, the refrigerator works continuously on DC operation (no thermostat control).

On AC operation, the temperature is controlled by a ther- mostat. The thermostat knob (C, in FIG. 8) should be set to position 4-5 in normal working conditions. If the ambient temperature is high and/or fresh food is put into the refrigerator you may set the refrigerator to a higher setting.”.

And for gas operation (in part) -“
1) Open the shutoff valve of the gas bottle. Check that there is enough gas.Open any on-board shutoff valve which is in the gas line to the refrigerator.
2) Open the lower vent at the rear of the refrigerator on the outside of the vehicle, and switch the electrical toggle switches A and B to the "OFF" position.
3) Turn the gas thermostat control (F) to the highest setting.”.

So, it sounds like there are two thermostats which are the common denominator for 120VDC and gas operation.
Have you located and adjusted those as pictured and described in the manual?
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Old 07-21-2021, 12:38 PM   #3
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Quote:
Originally Posted by MrMark52 View Post
Have you looked at the manual?

It says “ In the case of the RM4223, the refrigerator works continuously on DC operation (no thermostat control).

On AC operation, the temperature is controlled by a ther- mostat. The thermostat knob (C, in FIG. 8) should be set to position 4-5 in normal working conditions. If the ambient temperature is high and/or fresh food is put into the refrigerator you may set the refrigerator to a higher setting.”.

And for gas operation (in part) -“
1) Open the shutoff valve of the gas bottle. Check that there is enough gas.Open any on-board shutoff valve which is in the gas line to the refrigerator.
2) Open the lower vent at the rear of the refrigerator on the outside of the vehicle, and switch the electrical toggle switches A and B to the "OFF" position.
3) Turn the gas thermostat control (F) to the highest setting.”.

So, it sounds like there are two thermostats which are the common denominator for 120VDC and gas operation.
Have you located and adjusted those as pictured and described in the manual?
That pretty much sums it up^^^^^^^^^^

Turn AC t-stat to MAX and run it for 12 hrs
Then test GAS by turning Gas T-stat to MAX and run it again
*Open door to warm up fridge between the testing
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Old 07-21-2021, 10:27 PM   #4
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Yes, I've read the manual, tired it on max several times, and done this test as you both suggest. Still doesn't cool down enough. Other ideas?
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Old 07-21-2021, 11:09 PM   #5
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DC Element is 125W
AC Element is ALSO 125W ----120VAC/~115ohms/1.4A
GAS is 1040btu equivalent to 304W (Higher heat valve due to radiant heat transfer vs conduction heat transfer with elements)

AC T-stat on MAX...element should stay ON
Gas T-stat on MAX...flame should stay ON

Both AC and Gas use a 'thermocouple wire' from T-stats to fridge

Have you measured the AC Voltage AT terminal block?
Have you measured the AC Voltage from switch to t-stat?
Have you measured AC Voltage from t-stat to/thru element?
Have you measured the AC Element Resistance?
Pg 10 of this Parts List shows wiring for DC & AC Elements
https://www.gas-refrigerators.com/pdf/RM4223-parts.pdf



Gas...
Have you measured the LP System Pressure...manometer with 50% of other propane appliances on?
S/B 11"WC with fridge on gas

What does the GAS Flame look like....strong/blue and just reaching up into opening of flue?
Have you cleaned burner/orifice/flue-flue baffle?
Pg 11 of manual shows Gas Components/cleaning
https://www.bing.com/newtabredir?url...ser-Manual.pdf
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Old 07-22-2021, 06:54 AM   #6
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In addition to Old-biscuit’s comments above - and it doesn’t show in any of the documentation I’ve looked at so far -

Make sure the sensing element of the two thermostats are properly positioned and mounted as determined by the manufacturer.
In my old appliance servicing days, you’d be surprised at how many wall mounted sensing elements in ovens were knocked loose when the oven was being cleaned - the sensing elements need to monitor a greater mass than what air is (solution - reattach the sensing element to the clips).
I would expect the requirements for sensing would be the same on the refrigerator, taking into consideration the thermal variances from top to bottom of the surface the sensing element is mounted to (assuming it is mounted).
The variance’s can be handled by moving the sensing element vertically up or down, if possible (remember, heat travels up).

Not sure if both sensing elements are mounted together or separately, but worth taking a look at - check for being properly mounted and that if contact mounted that they have good thermal contact with what they are sensing.
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