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Dometic issue: Backfiring? SOLVED
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AZ_CreamPuff
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PostPosted: Wed Sep 27, 2017 10:27 pm    Post subject: Dometic issue: Backfiring? SOLVED Reply with quote

So trying to rehab the dometic because I would really like not to have to carry a cooler every where.

Pulled the fridge out and did the whole rehab procedure from the FAQ section and still have an issue. When I try to light the fridge I can only get a response once I have let off the gas button. Let off the gas, click a few more times, then poof, backfires out of the flue. I have tried pumping like crazy as well as pumping air from the bottom drain tube.

Anyone have any ideas?
    Code:


Last edited by AZ_CreamPuff on Fri Sep 29, 2017 4:39 pm; edited 1 time in total
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atomatom
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PostPosted: Wed Sep 27, 2017 10:34 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

the path to dometic bliss is 12v or 110v heating of the pipe. after that, very easy to start.

yes, there is a lot else that could be crusty, but heat the pipe, and you will see it light.
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PostPosted: Thu Sep 28, 2017 4:38 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

If you have an electric pump that you can reverse the flow from pump to suck? Try it in the drain pipe.
Sounds that you do not have enough air in the burner chamber.
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PostPosted: Thu Sep 28, 2017 6:04 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

atomatom wrote:
the path to dometic bliss is 12v or 110v heating of the pipe. after that, very easy to start.

yes, there is a lot else that could be crusty, but heat the pipe, and you will see it light.


Very Happy Very Happy Very Happy
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PostPosted: Thu Sep 28, 2017 7:21 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

If you hear it pop, it is flooded. Before it popped, it was even worse flooded.
Let it sit 10 minutes and try again. You cannot give it gas when it is not lit. You have to be hitting the sparker immediately as you give it gas.

If you run it on 12 volts or 110 for 10-15 minutes that heats the element and makes warm air rise and pulls in fresh air to the chamber. Some people's fridges light fine without doing this, but many won't. Just do it and it will light on the first try.
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PostPosted: Thu Sep 28, 2017 7:39 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Just on a hunch are you lighting while inside a garage? I have always found lighting while inside is more difficult without a LOT of pumping or an electric pump.
Good tip about preheating and creating a draft.
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PostPosted: Thu Sep 28, 2017 10:56 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Adding to what others said so far:
- Double-check that the little air pump and especially the one-way valve in the air circuit are working properly. From experience, lighting a warm fridge with a stuck one-way valve is pretty much impossible.
- Double-check that your igniter is working correctly, and that it sparks at the right place. The tricky part is that not everyone agree on where the right place is. My pick is on the gas diffuser, not on the thermocouple.

If you have to pull the fridge again, I'd suggest to replace the igniter by an electronic one, as described here. Automatic reignition if the flame blows out, real-time notification that the flame is lit (when the igniter stops sparking), much quieter, there's a lot to love for $30-$50.

Also, since you're somewhat new here, I suspect that you may not have that much experience lighting these fridges. The process is a bit tricky, even with correctly tuned fridges. You may want to double-check that your technique is correct with a known working fridge, or asking someone to watch you lighting yours.
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PostPosted: Thu Sep 28, 2017 11:20 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

I would remove the fridge and blow compressed air into the gas lines to make sure they are clear. Also triple check that the burner and pilot hole is clear (I know you said you did this already but check again). Maybe run a single string of copper wire through the hole.

I ran across this issue with my fridge. It kept back firing on me so I decided to use the GoWesty cooling system pressure tool to pump air into the vent. I noticed that the more air the better, so pump a lot of air into the chamber using another pump and try to ignite.

Like others have mentioned, it seems to be a lot easier to light once it is warm. I had my fridge running one day and the flame went out after a windy drive so I tried to reignite it right away. It light with one try.

I watched a lot of YouTube videos on how to operate the fridge on propane. Not sure if you've done this or not but I recommend it.
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PostPosted: Thu Sep 28, 2017 1:02 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

jmranger wrote:

- Double-check that your igniter is working correctly, and that it sparks at the right place. The tricky part is that not everyone agree on where the right place is. My pick is on the gas diffuser, not on the thermocouple.




link to image from Dometic service manual page showing position of igniter:

https://photos.app.goo.gl/6pC4klC0bx9KXxN53
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PostPosted: Thu Sep 28, 2017 7:00 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Appreciate all the advice. Ran the fridge on 120 for an hour or so and it fired with gas button depressed (which I didn't before) although the pilot light didn't stay lit. Gasket for the flame box was a little iffy so made a new one out of some bike tire rubber, and poked the jet with a single strand of copper. By the time I got that all done and in the fridge parts had all cooled down. Currently have her back on 120 and will try again later.

If no luck I'll take it apart, again, and blast the propane lines with compressed air. It is firing though so I'm pretty sure im getting fuel into the chamber. Good spark as well, looks exactly like the diagram and I can see the spark through the peep hole

Also fridge is still out. Hooked it up to the BBQ propane. I'll also give the coolant pump a try, gowesty got me on that one too
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PostPosted: Thu Sep 28, 2017 8:32 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

AZ_CreamPuff wrote:
A....Gasket for the flame box was a little iffy so made a new one out of some bike tire rubber,



That burner box can get fairly hot. I realize the OEM orange-red gasket may be of a similar material but would suggest using red hi-temp RTV or similar to seal the box. That said, maybe tire rubber potentially sees more heat?
< shrugs >

Neil.
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PostPosted: Thu Sep 28, 2017 8:52 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Yeah, I was concerned about that too. Rehab guide said inner tube works too. Might change it for good measure if I can get it lit. Still no dice. Watched a few you tube videos, can get it to pop no problem but that's about it. These refers are frustrating!
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PostPosted: Thu Sep 28, 2017 9:56 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

1990 model fridge. Perfect working condition. Includes aux air pump for lighting under difficult conditions. $100 prefer pickup in Sacramento CA. Freshly cleaned and serviced. Collecting dust.
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PostPosted: Thu Sep 28, 2017 11:53 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

I completely went through our 1990 Dometic using some newer parts - new auto ignitor, replaced the thermocouple from a known working fridge (this keeps the gas valve open after you've let off the gas button and flame is proved), re-lubed the air pump so it actually did something (there's a thread on a mod to the pump too somewhere - you enlarge the hole a bit). Cleaned all the flue ways. Careful with the clearing of the orifice, may have enlarged it a tad and getting to much gas which is throwing the mix off till enough makes it into the flue to ignite - "pop!". Our works great now, lights easy and does a pretty good job of keeping things "cool". Will make ice if it's less then 60° out Very Happy

Also LP gas that has been sitting for sometime can be pretty stubborn. Make sure your stove burners are burning nice and blue w/o yellow or orange.

All that said...
dgbeatty wrote:
1990 model fridge. Perfect working condition. Includes aux air pump for lighting under difficult conditions. $100 prefer pickup in Sacramento CA. Freshly cleaned and serviced. Collecting dust.


I'd jump on that if your going to stick to LP. I probably spent close to $100 refabbing ours.
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PostPosted: Fri Sep 29, 2017 1:16 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

There's no doubt that how much a fridge has been abused (e.g. run on to much of an angle) plays into how well it works (due to chemical interactions, or lack thereof, beyond my means of understanding) but I've gotten at least two old 182 fridges to make ice; when I got my first Westy with a 182A, it worked only on AC mode. It eventually worked on all 3 just fine save for the occasional blow out on LP while driving or camping in really stiff cross winds. Yes, if it got too warm inside the van, and there was too little cold food inside, or I parked with the fridge side exposed to midday Summer sun, they would perform poorly, but I think my point is that if the fridge is repaired, it can work ok on all modes and under the right conditions, make ice easily. In terms of the actual "guts", condenser etc., where one draws the line in terms of bailing on a given absorption fridge, I don't know. Not sure how one tests that kind of thing. In terms of investing too much money in a loser fridge, "Caveat Emptor". That said, i did not invest much money in any of my Domestics. Just my time, some wires, switches, fans and a lot of head scratching and searching.

Neil.

My original 182A Dometic doing quite fine back in 2009 during a Fall trip in Idaho and Oregon. If I'd traveled longer, exchanged less food so often (drank less) that cooling unit would be covered in ice frost. Notes from that time

"Happy Dometic. Behaved well in spite of mid 90's (highest temp in van window open driving) Highest fridge temp 42F. Weather was hot at times. Used all 3 fans during those times. [all 3 being fan at rear exterior cooling fins, fan inside fridge, "city water" fan] Leaving factory fan on seemed to help a lot. [I had wired a bypass switch to the fan at fridge exterior rear] Well that and the pre cooled beers, and NOT parking with fridge side toward sun."

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Fri Sep 29, 2017 9:41 am    Post subject: Re: Dometic issue: Backfiring? Reply with quote

AZ_CreamPuff wrote:
Yeah, I was concerned about that too. Rehab guide said inner tube works too. Might change it for good measure if I can get it lit. Still no dice. Watched a few you tube videos, can get it to pop no problem but that's about it. These refers are frustrating!


You don't want to hear it pop. When they light normally, it does not pop. The popping is the result of the chamber being flooded. I assume you blew out the intake and exhaust hoses with a shop vac? That is usually a big help. I would guess you are doing something wrong when you try to light it.
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PostPosted: Fri Sep 29, 2017 2:02 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Appreciate the offer on the fridge! I'm in AZ and not sure if I'll be in Sacramento anytime soon :-/

What about this. Could my BBQ regulator be supplying to much pressure to the system? This particular regulator is used to supply a turkey fryer I have. Might throw it back into the van this evening and see if my luck changes.
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PostPosted: Fri Sep 29, 2017 3:16 pm    Post subject: Re: Dometic issue: Backfiring? Reply with quote

Are the intake and exhaust pipes totally clear? There are dimples on the exhaust pipe that could catch debris.

Image links to one of my old 182A fridges showing "dimples". 182B should have same:

https://photos.app.goo.gl/WShOVpybj4S3goxr1

https://photos.app.goo.gl/cGPogKvEnemaBQ8p1
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PostPosted: Fri Sep 29, 2017 4:39 pm    Post subject: Re: Dometic issue: Backfiring? SOLVED Reply with quote

Update so I don't leave this thread hanging. I think my suspicion was right with the BBQ regulator being to high of psi. For what it's worth the BBQ regulator is 15 psi. I believe the gas being delivered inside is less than that. Hooked it back up in the van and lit up first try. Thanka for all the help. Hopefully this thread helps someone in the future trying to test the fridge outside of the van
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PostPosted: Fri Sep 29, 2017 4:55 pm    Post subject: Re: Dometic issue: Backfiring? SOLVED Reply with quote

AZ_CreamPuff wrote:
Update so I don't leave this thread hanging. I think my suspicion was right with the BBQ regulator being to high of psi. For what it's worth the BBQ regulator is 15 psi.


Yes; if you're going to use a BBQ regulator to bench test, it needs to be a low pressure version (which my new BBQ regulator is, but boy does it put out the pressure compared to the clogged up old one!).

Good to hear your Dometic is now working. Very Happy
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