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Post by montereykeys on May 20, 2023 14:04:49 GMT 10
We have a dometic 2553 3 way fridge in the caravan. It has always worked great. Suddenly halfway through our last trip it developed a problem running on gas.It will not cool below 5 degrees in the fridge even when the thermostat is turned to max, which would normally freeze everything. There is no problem igniting the gas and it stays alight ok. However the flame indicator gauge on the front of the fridge only goes as far as the center line without going into the green. 12 volt and 240 volt settings work perfectly and respond to thermostat adjustments.
The gas pressure at the test point in front of the burner is the correct 11 inches so I assume that rules out the regulator. I have cleaned the jet (orifice) and burner by soaking in meths and blowing out with compressed air. The flue and baffle look clean.
I am starting to think the problem is with the thermostat but reluctant to spend $200+ without being confident that is the problem. Any suggestions as to the cause would be greatly appreciated.
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Post by Old Techo on May 20, 2023 15:17:04 GMT 10
G'day and welcome Montereykeys
You seemed to have 'cut to the chase' with tests done so far.
Confirming the gas pressure right at the burner rules out gas supply issues.
The flame indicator, which is just a small electrical meter measuring the voltage output of the thermocouple, suggests not enough gas heat. I would only assess the accuracy of said meter if I knew that it displayed a noticeably higher reading before the fault situation. However, it makes sense as a weaker gas flame would explain your issue.
If you are certain that the jet is 100% clean then not a lot left in my mind.
If it was thermostat related I think that can only be in 2 ways. It never permits enough gas flow or restricts flow when the thermostat thinks the fridge is cold enough. Either way your pressure test would show that if you monitored it for long enough. If the pressure never drops then not a thermostat issue.
The last thing left in my mind is the flame size and shape is inadequate despite the cleaned jet.
Thus, the sum total of my contribution is... I think the thermostat can readily be ruled out by monitoring gas pressure at the burner test point.
We have a gas professional on the forum so I'll see if I can get his attention
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Post by GerryP on May 20, 2023 15:50:45 GMT 10
Are you sure the jet is 100% clean? The best way is to place it in boiling water as this will melt any wax that may be lodged in the jet. It's possible that metho won't do the same. Blow out with compressed air straight out of the boiling water. Do not be tempted to use a needle or wire as the jet is ceramic and easily damaged. Good luck. 👌
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Post by montereykeys on May 20, 2023 17:07:09 GMT 10
Thanks for the response Old Techo and Gerry, I'll be pleased if it isn't the thermostat. The flame indicator would always enter about 30% into the green sector immediately before this problem began. I will try boiling the jet to see if any improvement.
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Post by Frank and Brenda on May 20, 2023 20:50:01 GMT 10
I hated my 3 way so changed over to a 12v compressor fridge but while I had the 3 way one of the things I had to do was blow the crud out of the gas line It needs to be done on a warm day as it's in liquid form when warm but turns to sludge when cold Disconnect the line near the fridge before the isolation tap and at the regulator and blow compressed air through the line from the regulator side Oh and welcome to the friendly forum, where you don't have to be twisted but it helps
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Post by Old Techo on May 21, 2023 9:32:19 GMT 10
Frank,
Because of my Aviation background I insist upon redundancy i.e. if a system fails there is an alternative.
That is why I much prefer a 3-way fridge. It has 2 heating elements and runs on gas when there is no or very limited electrical power.
Yes, they do have some annoying habits but I can live with them.
Re the gunk clogged gas line... yes, I've had that twice in 19 years. In my case the effect could be seen on the cook-top with the gas flame pulsating as the oily gunk moved up/down the vertical part of the gas line. I didn't include this consideration in my suggestions here as gas pressure at the fridge was reported as correct.
From one 'twisted' member to another Frank
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Post by jr on May 21, 2023 9:38:57 GMT 10
I did reply to your post on the other forum and missed your comment that the fridge is ok on 240V. You say there is 11” water gauge pressure, is that with the fridge gas flame on?
At the fridge flue outlet can you feel quite a bit of warmth.
OT should know is it the same thermostat for gas and 240V.
JR
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Post by montereykeys on May 21, 2023 9:39:24 GMT 10
I hated my 3 way so changed over to a 12v compressor fridge but while I had the 3 way one of the things I had to do was blow the crud out of the gas line It needs to be done on a warm day as it's in liquid form when warm but turns to sludge when cold Disconnect the line near the fridge before the isolation tap and at the regulator and blow compressed air through the line from the regulator side Oh and welcome to the friendly forum, where you don't have to be twisted but it helps Thanks, when it warms up I'll blow out the gas line to see if it helps.
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Post by montereykeys on May 21, 2023 9:43:56 GMT 10
I did reply to your post on the other forum and missed your comment that the fridge is ok on 240V. You say there is 11” water gauge pressure, is that measurement at the fridge test point and with the fridge gas on? At the fridge flue outlet can you feel quite a bit of warmth. OT should know is it the same thermostat for gas and 240V. JR Confirm 11" pressure measured at the fridge test point with the fridge running on gas. Yes, warm at the flue outlet. Unless I missed something there's only one thermostat in the 2553 fridge.
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Post by jr on May 21, 2023 13:33:09 GMT 10
From the attached photo of the RM2553 thermostat looks like it does the electric and gas all in one. It will have a bellows that will turn the gas supply up and down and also operate contacts for the electric. As the 240V is OK its hard to understand that the gas would not be OK.
Only thing left is heat transfer in the flue and you have already checked the little twisted metal thing in the flue is in place. JR
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Post by legendts on May 21, 2023 16:39:06 GMT 10
That is why I much prefer a 3-way fridge. It has 2 heating elements and runs on gas when there is no or very limited electrical power.
Yes, they do have some annoying habits but I can live with them.
Re the gunk clogged gas line
We prefer our 3 way too and never had an issue with it not cooling in hot climes. We do have two quite large opening doors at the back with two hats on the roof. Haven’t had an issue with clogged lines in our 23 years with the van but will add that to the storage memory 😉.
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Post by loub on May 22, 2023 7:57:47 GMT 10
Me too.Our AES works well in all conditions, I think if it's T rated and installed properly with the vents and also a roof vent it seems to make it all work well.
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Post by dieseltojo on May 22, 2023 8:03:43 GMT 10
I have not had much to do with fridge problems but mine was bought in 2003 and still runs well.
On one occasion I helped a camper that had tried to fix a similar problem and all it was , the pilot flame was not directly under the themo line and not getting full heat.
The flame needs careful placement. If the flame has a lot of yellow in the colour it indicates the gas is not adjusted well. I have also had gas bottles that when empty had a fair bit of fluid in them which is simply residue from a long time of use. I would try a newly filled bottle if you bottle is pretty old.
Just a point of interest.....
Auto gas can have a lot of gunk in the gas especially in a cold or high altitude climate. The calorific value of the gas is subject to change due to in the size of a burner in cold areas.
These consideration are usually not present at most sea level areas though. I have had to tip an empty gas bottle upside down with the valve open to drain it. If there is a black sooty smoke in the flame, that is the sign of tarry oily residue in a bottle.
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rvgasguy
On the way up
Posts: 18
Location: Greater Brisbane (Cause it's Great)
1st name: Lindsay
Tow/Motorhome: Hilux work ute
Caravan: Workin on em'
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Post by rvgasguy on May 23, 2023 16:39:25 GMT 10
It looks like you've covered most of it.
240v and LPG do share the thermostat, so shouldn't be that if 240v is ok. OT covered contamination. Most times the contamination is too heavy to be pushed up hill far enough to affect an appliance directly, but It can block the pipework to them. Contamination normally won't affect the fridge due to the small amount of gas required, unless it has total blockage.
Check the burner itself, they have a grill type burner and the grill sections can rust and break out and it won't burn correctly. (I've just ordered for a customer, that exact burner because his is broken)
Also, I know you've cleaned the jet, but have a really good look at it. Sometimes crap sticks in there and can only be seen under magnification. I use a jewelers eye piece, available cheap on line, don't go too big, only about 5 - 10 times mag. It's amazing what can still stay in there after having 100 psi up it. I once replaced what I thought was a perfectly clean jet and no more problems. (That's when I bought the eye piece)
Also, after removing the jet, let some gas flow through the pipe that supplies the jet, (push the gas button) to blow any other crap out.
Not much left.
Good Luck!
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Post by montereykeys on May 23, 2023 17:34:33 GMT 10
Thanks for all the help. Looks like I have got lucky. I cleaned the jet again soaking it in meths for an hour or two. Ditto the burner. I also checked the flue and baffle again. But what probably fixed it was what I found in the adapter at the end of the flue, which I hadn't really looked at before, a few mud wasps nests which I cleaned out. Now the needle in the flame meter goes to the middle of the green and all seems well.
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