Domestic 3804 Not Cold On Gas

[dano73]

I have a 1990 dometic that works fine on electric, but barely works on gas. A few weeks ago it lasted about a day on gas, now it melts down within a few hours. The cooling unit is spotless, I mean no rust, barely looks like it was ever used. The regulator was replaced, the pressure at the burner is 12, the burner is spotless, no rust in it. The flame is a strong blue, never goes out , and the chimney temp, checked with an IR thermometer is the same wether on gas or electric. The chimney is clean as far as I can tell, I've blown air up it, and using a mirror, looks clean inside. I have cleaned the orifice with alcohol, made no difference, and the burner is in position directly under the chimney. I have owned this for about 4 yrs and it never really worked well on gas, now it's really getting unuseable, unless it's plugged in. Oh and all the other gas appliances work fine. What's left??the board??

[dougrainer]

dano73 wrote:
No Doug. I presented my problem and thanked all for their help. I feel the same way you do about the flue and baffle,, but people who are wiser than me, perhaps could tell me what they thought and I appreciate it. It's not so simple, ok, I get it. Sorry if I ruffled ur feathers.

You did not ruffle my feathers. I KNOW from experience what the next step should be. Doing anything else is a waste of time. Just trying to keep you from wasting your time on things that will not fix your problem. Doug

[SidecarFlip]

oh boy....

[dano73]

No Doug. I presented my problem and thanked all for their help. I feel the same way you do about the flue and baffle,, but people who are wiser than me, perhaps could tell me what they thought and I appreciate it. It's not so simple, ok, I get it. Sorry if I ruffled ur feathers.

[dano73]

U sure about that? How do u keep it square? Then ur moving the burner farther away from the orifice? Shouldn't that distance remain the same?

[dougrainer]

dano73 wrote:
Thanks for all the replies. General consensus is the fchimney needs to be cleaned. The dometic manual says the burner needs to be centrally located under the flue. Biscuit, you said it can't be touching the sides. My flame looks like that, but I would say it needs to move right about an 1/8 in. I've looked in there, and don't see any sideways adjustment. I do see screws with a slot that the circuit board is stewed to, but loosening 3 does nothing, I'm thinking there's one more behind the orifice assembly, or better yet, can anyone tell me how to slide the burner over?. Pulling the fridge out right now is prolly not gonna happen. Have a trip planned for next week, in the process of finding styrofoam coolers that will fit in the fridge. Lol.

Your problem has now entered the stage where you WANT it to be simple. It is NOT. You need to pull the refer to verify the condition of the baffle and if it has one. The flame burner mount is preset and almost impossible to be mounted OFF. Your flue does not need cleaned. If it was dirty enough to stop cooling then it would block the exhaust and then go out. I have NEVER had to pull a refer to clean the flue. I use a angled air nozzle and blow up from the bottom above the burner. That will clean any possible dirt or rust build up. Go on your trip and then pull the refer when you get back. Doug

[SidecarFlip]

The burner mount is sheet metal, you tweak it a bit....

[dano73]

Thanks for all the replies. General consensus is the fchimney needs to be cleaned. The dometic manual says the burner needs to be centrally located under the flue. Biscuit, you said it can't be touching the sides. My flame looks like that, but I would say it needs to move right about an 1/8 in. I've looked in there, and don't see any sideways adjustment. I do see screws with a slot that the circuit board is stewed to, but loosening 3 does nothing, I'm thinking there's one more behind the orifice assembly, or better yet, can anyone tell me how to slide the burner over?. Pulling the fridge out right now is prolly not gonna happen. Have a trip planned for next week, in the process of finding styrofoam coolers that will fit in the fridge. Lol.

[dougrainer]

If it works on 120 but not on Gas and everything on the gas side has been checked and it is at spec, then the ONLY thing left is the Baffle. Odds are, there is NO baffle or the Baffle has been burnt up from 27 years of use. Your only recourse is to pull the refer and pull the baffle and see what it looks like. The baffle is a spiral piece of metal and the spiral causes the flame to disburse in a round fashion to correctly heat the bottom boiler tube. Another cause of NO Baffle is, the cooling unit has been replaced and Dometic Cooling units do not come with new baffles and inexperienced people fail to transfer the baffle from the old to new cooling unit. Doug

[SidecarFlip]

dano73 wrote:
I have taken the top cover off my trailer and there is no way I can access the top of the chimney. There is a raised rectangular screened port that allows the heat out, but no access to the top of the chimney. I've had many old trailers, but have never had to clean the flue, and the only possible way to access it is to take the fridge out of the cabinet. I have tapped on the chimney, and gotten some light rust, nothing crazy, no big chunks or flakes, what I would consider normal.. And if there is a blockage, which I doubt, why would the external temp of the chimney, be the same as it is when it's plugged in?

It appears to me that you will have to (access the baffle and pull it) whether you want to or not (even if it means pulling the fridge out on the cavity.

My gut feeling is, it's sooted up and needs cleaning as well as the chimmney inside (with a bottle brush, from the top down with the burner removed, because the junk is going to come out...big time.

As Mr. Biscuit points out, the temp is higher on propane than it is on the Mullion tube, not equal.

I think you have a clogged boiler.

Lets be specific, it's only one tube for the flame chimney (which is why there is a baffle in it and one tube carries the ammonia solution and they aew welded together.

[Old-Biscuit]

Section F: Page 63 thru 71 --- Dometic RM3804
http://www.wanderlodgegurus.com/database/WanderlodgeForum/Files/Dometic%20Diagnostics.pdf


In order for propane to properly cool the Flue has to be clean, the Flue Baffle has to be clean (It is the means by which heat generated by flame is transferred to perk tube)....stack temp S/B 350* PLUS (Electric heat is 330*F)

Flame has to be Strong steady BLUE that reaches just inside flue opening and Centered (can not be touching sides of flue)

Clean burner slots, clean orifice, clean flue/flue baffle and GOOD ventilation...and proper LP System Pressure (11"WC---0.4 psi)

Does it look like this??

[Gjac]

Have you removed the burner tube to look inside some times fine rust can build up inside the tube and block the flow of propane. If the tube is original the slots can enlarge over the years of repeated cleaning with a wire brush allowing more air to propane weakening the flame. I would not think it is your board.

[wnjj]

Is the baffle still there and installed correctly? It's used to slow the rising heat down to thoroughly heat the tubes. Maybe the exhaust temperature is correct but the middle and lower sections aren't? The electric element spreads the heat automatically.

[SidecarFlip]

Got me. Maybe it's time for a Danfoss compressor fridge.

[dano73]

I have taken the top cover off my trailer and there is no way I can access the top of the chimney. There is a raised rectangular screened port that allows the heat out, but no access to the top of the chimney. I've had many old trailers, but have never had to clean the flue, and the only possible way to access it is to take the fridge out of the cabinet. I have tapped on the chimney, and gotten some light rust, nothing crazy, no big chunks or flakes, what I would consider normal.. And if there is a blockage, which I doubt, why would the external temp of the chimney, be the same as it is when it's plugged in?