Forum Discussion

btcruzer's avatar
btcruzer
Explorer
Jul 11, 2020

Dometic fridge woes.

I have a Dometic model RM2453 3-way fridge that works in all 3 modes but the LP mode is a problem. It always ignites and burns clean. However I don't believe that the flame is hot enough. I've always heard that LP mode usually cools better than electric and that has been my experience with several different RVs. But this one is different.
This model does not use a "pilot Light" - instead it has a thermostat controlled gas valve with two passages. One is the bypass that allows a small flow of LP to flow in order to maintain the pilot light. The other is is the full flow passage that should cause a larger flame when the thermostat calls for cooling. The thermostat also controls a simple off/on switch in the electric mode. I have tested the electric side and determined that the thermostat does turn the electric on and off as needed.
I have measured the temp of the boiler tube at the same spot (just above the top of the flue) in both electric and LP mode. Electric is hotter.
The thermostat has 9 settings -
OFF ( not really off but bypass mode)
1 through 7 are temp settings - 1 warmest and 7 coldest
MAX is full time operation not controlled by the thermostat.

I've read that there is a visible difference in the flame height in the bypass and full operation. I have observed the flame while in the OFF position (bypass mode) and then someone switching the thermostat to all the other settings. No difference. I've also heard and observed that you can hear the flame. Not this one.

The burner assembly has been removed and cleaned several times. The jet (#43 per Dometic) has been removed soaked, cleaned and blown dry several times. The flue has been swabbed full length several times.

I have replaced the 2-stage LP regulator. I have measured the LP gas pressure with a manometer. Initial pressure was 13 inches of water. Dometic manual says 11 inches. Adjusted pressure and observed pressure for probably an hour in operation -- never varied.

I replaced the thermostat. No change.

I am out of ideas. The LP pressure is taken within an inch of the jet. Seems to me that the proper pressure through the specified jet should produce the full flame. What am I missing?



I'm convinced that the ther
  • dougrainer's avatar
    dougrainer
    Nomad
    Jul 11, 2020
    1. The Correct way to verify the LP pressure is at the Port just behind the Orifice. THAT will tell you if the Tstat is allowing the full 11.5 inches WC to the burner. When in BYPASS mode the Pressure will drop to Pilot flame pressure.
    2. FILTER A filter is located in the inlet fitting to the thermostat. The filter can become saturated and cause a restriction to gas flow. If you suspect a restriction, first verify the thermostat and bypass screw are good. THERMOSTATLP GAS MODE The thermostat is calibrated by the manufacturer so that at mid-range the cabinet temperature should be approximately 40 degrees Fahrenheit. To check the calibration of the thermostat, place a container of water in the cabinet of the refrigerator and operate at mid-range setting until the thermostat is satisfied. Check the temperature of the water. It should be approximately40 degrees. To check the thermostat for proper g a s flow, set the thermostat to maximum and check the gas pressure at the pressure test port. It should be line pressure, between water column. If you have less than 11 inches of water column pressure, the next step would be to shut off the gas supply and remove the bypass screw. Then install a bypass screw that does not have the small o-ring on it. Next, turn on the gas supply and take a reading. If the manometer now reads 11 inches of water column, the thermostat is defective and must be replaced. If the bypass screw test shows no change in pressure, the problem lies in the filter, the shut-off valve or the gas supply.
    3. Since you have replaced the tstat, That FILTER is what I would suspect is the problem. Also, are you POSITIVE that you did not kink or break the Metal Sensor Cappillary tube that runs to the Evaporator fins? If it loses its gas charge it will cause your type problem.
  • btcruzer's avatar
    btcruzer
    Explorer
    Jul 11, 2020
    this fridge does not have an electruc gas shut off valve.Only shutoff is a manual cutoff at the LP line.
  • b17drvr's avatar
    b17drvr
    Explorer
    Jul 11, 2020
    Do the Dutch air mod. It turned mine into a real refrigerator. No more problems.

    https://jc-refrigeration.com/
  • ernie1's avatar
    ernie1
    Explorer
    Jul 11, 2020
    I have a Dometic RML8555 3 way refrigerator and have the same problem except that mine came like that brand new from the rv dealer. Worse, I have two friends who have the very same rv that were purchased new about a year before and a year after me who have the same problem and contacts with Dometic makes things worse. They tell them to take it in for diagnosis at an authorized Dometic dealer who does work on them and charges the customer for the work because Dometic says it's not covered under the warranty! I run my fridge on 110ac as it comes from the inverter because it gets colder than the lp mode.

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