Dometic fridge woes.

[btcruzer]

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

[btcruzer]

I guess so far all I have found is that the thing works well on a/c. The whole idea of buying the Roadtrek was to be able to boondock at race tracks for 3 or 4 days without running a gen. So I am particularly interested in the LP option.

At 5 PM I switched to LP mode. Nothing else was changed. Except the temp inside the rv has dropped from 105 degrees to 94. Within 5 minutes the refer temp increased to 27. The condenser tube I had been monitoring for temp dropped from 114 to 107. I was running a small fan on the condenser fins but turned it off when switching to gas. Without the fan the condenser tube was over 130 degrees at times. Time will tell.

[btcruzer]

I'm thinkin the refer is good. Was worried about a damaged cooling unit.

At 8 this AM I moved the selector from MAX to 7 .. the temp has stayed at 26 or below with inside RV temps as high as 101. RV parked in full sun with back of fridge to the sun.

Been measuring the the temp of the tube above the evaporator. Some advertisement for a product to protect from overheating says fans on this tube should start at 139 degrees and shut off at 109. Mine has done on its own without fans but I can lower the temp with a small fan.

I've tried all kinds of fans, locations and baffles... nothing seemed to help the

This tube never got very hot on gas. Gonna let the thing run until this evening and switch it back to LP with no other changes and let it run for 24 hrs. Maybe now that it is hot the LP mode can keep it hot.

Earlier while messing with all this the refer was empty. Sometime yesterday I put 2 gallons of water (room temp)in. That was there through the night and was not frozen this AM even though the box temp was 23. Around 8 this AM i opened the box and added 2 frozen blue packs and 5 small palm sized cold packs. The temp went to 25 but was back down to 23 shortly. . have maintained temps within 3 degrees while interior RV temps have increased almost 30 degrees.

Been interesting --- will report tomorrow.

[dougrainer]

Your refer is just fine. The temps are actually better than expected. I would now switch to LP and see if the refer maintains that 23 to 30 degrees over 24 hours. If NOT, then I suspect your new tstat is defective. Doug

[ernie1]

btcruzer: thanks for the info

[btcruzer]

Doug--- yesterday and last night were cooler than it has been laterly... The fridge ran on A/C since 2 pm yesterday until now. the temp inside the fridge (not freezer) is 23 degrees. The temp selector is set to MAX that bypasses temperature controls and the fridge runs full tilt - always on. Temps inside the RV yesterday was average maybe 85 degrees This AM it is 73 so far.

on the LP side -- I should be able to get the fridge to lower the flame by setting the t'stat to OFF. That is supposed to keep the flame at a pilot light size. Then the MAX setting is supposed to keep the flame at full height full time bypassing any temp controls. Todays 23 degree temp was on A/C at MAX setting. I have observed the flame while the setting was on OFF and had someone then switch the setting to MAX ... no difference in the appearance of the flame.

I have read that once can hear the difference in the flame sizes. I cannot hear this flame at all. I can hear the flame in my other RV without removing the vent. I guess a smaller fridge might need a smaller flame.

I have read that extended use in the MAX setting can cause damage to the cooling unit by overheating it. If this has been damaged could the thing produce the 23 degrees I getting on electric? Or would it just taker longer and not be able to maintain the cold?

I guess that "I have read..." quite a bit. Guess I just have not yet read that little gem of info that I need.

[btcruzer]

Tom M ..actually I did check the filter - it looked brand NEW - because it IS. I looked at before I installed the NEW t'stat. It is located in the inlet of the t'stat. I also looked at the filter in the removed t'stat... didn't look much different from the new. EARNIE1 ... the filter is just a small wad of what looks like cotton (maybe a little larger than a pencil eraser) pushed into the inlet of the t'stat. On this particular fridge the controls and most of the LP plumbing is located on top of the fridge and the fridge sits in a compartment that allows no access to them. The only things accessible from the outside vent is the primary shutoff valve and the burner tube ( along with the orifice, igniter, and thermocouple). This fridge has to be disconnected from the LP supply, unscrewed, then slid foreward into the RV in order to access the filter or most anything else.

[ernie1]

How does one access the filter to the thermostat? Just unscrew the gas line connection? I see a fitting on the gas line that is screwed into the thermostat and has red thread sealer on it.

[dougrainer]

Tom_M wrote:
It looks like you haven't checked the filter as dougrainer suggested. A few years ago a fellow camper was almost to the point of replacing his fridge but luckily he checked the propane line. It was full of oil.

Bingo, I was going to mention this. Usually, when I had this type weird problem I would hook the Shop LP tank to the refer and bypass the RV LP system to see if it worked correctly. Have you actually verified the refer operates to temp on 120 volt? What were the lower temp? Below 50 degrees? Me thinks the Flame is at correct HEATING height. Because the refer is warm inside, you cannot get the Flame to go to bypass mode?. By getting the refer to temp on 120, then start on LP and watch the flame when you open the refer door to allow hot air inside. Once the Capillary tube on the fins starts to warm up, the Bypass flame will then get larger to show the tstat and LP system is doing its job. Last, when ON LP, how cold does the refer actually get? Doug

PS how large LP tank does the RV have and when was the last time it was either purged and filled or just filled?

[Tom_M1]

It looks like you haven't checked the filter as dougrainer suggested. A few years ago a fellow camper was almost to the point of replacing his fridge but luckily he checked the propane line. It was full of oil.

[trailrider]

I would put in a new orifice. Cleaning it doesn't mean it is as good as new. Like carburetor jets, sometimes you can't get them clean.

[btcruzer]

with the temps here in Missouri - I'm putting this problem on the back burner. We have a trip (different camper) coming up soon. When the weather cools, I'm planning to remove the fridge and systematically disassemble each piece of the LP plumbing and blow out in reverse direction of flow. Then I am totally out of ideas. The ROADTREK might be available for sale by September.

Thanks to all for suggestions and info.

[btcruzer]

Doug. Yes I remove the baffle each time I swabbed the flue. Looks good - no rust - in tact, no burnt or missing corners, . Had several RVs, this is the best looking one I've seen. Probably because it havsen't been really hot.

[dougrainer]

What about the Baffle? You did not respond. Doug

[btcruzer]

enblethen Yes, I agree that proper pressure does not guarantee sufficient flow.

And it seems that I have insufficient flow (volume). The thermostats method of controlling temp is to allow more flow when cooling is required. That is done by opening up a second passage (sort of a passing lane). If, indeed, the 'stat is opening that second passage then there must be a restriction (unauthorized) somewhere between the regulator and the orifice.
I bought the RV used and don't know if the fridge EVER really worked well on LP. It does well on A/C.

lunch time --- later

[enblethen]

Just because you have pressure at the test port doesn't mean you have sufficient volume.