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Dometic fridge Head scratcher
#1
            This has been a head scratcher. No one has seen this happen before so have not been able to resolve the problem.

My burner on the fridge gets a build up of some type of matter that starts at the igniter rod and grows to and makes contact with the thermocouple. Fridge runs ok until it is purposely shut off such as for cleaning then won't relight because it is now shorted between the ignitor and thermocouple.
Thought it might be something in the gas but I use the same gas supply for another camper fridge which burns clean.

This started a couple years ago and seems to be increasing its happening in a shorter time. Had to get up at 3am this morning to clean the stuff for re-ignition and 8 hrs later there was almost half the distance built up again see pic.

Attaching 2 pictures.

Brad
1988 40 ft 8v92 newell
Coach name Big Blue
25 ft Haulmark car hauler with Andersen Anti sway
2012 Toyota FJ Cruiser.
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#2
Brad

I suspect a grounding issue. The thermocouple has a slight charge on it which attracts ionized soot particles.

It's a common technology for depositing coatings
Richard and Rhonda Entrekin
99 Newell, 512
Subaru Outback Toad
Rhonda's FB (Rhonda Duggan Entrekin)
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#3
Where do I start to check such a thing? Maybe replacing the electrode?
1988 40 ft 8v92 newell
Coach name Big Blue
25 ft Haulmark car hauler with Andersen Anti sway
2012 Toyota FJ Cruiser.
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#4
Replace the electrode and run a ground wire from the fridge fame to a good ground on the frame
Richard and Rhonda Entrekin
99 Newell, 512
Subaru Outback Toad
Rhonda's FB (Rhonda Duggan Entrekin)
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#5
I agree with Richard about the grounding being the likely culprit. I would wait to replace the electrode until after I had fixed the ground and seen how it works, after all once you clean the gunk off it seems to work just fine as you've described.
Jon Kabbe
1993 coach 337 with Civic towed
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#6
Looks like a carbon build up. Might be burning too rich. See if the air intake at mixing area is partially blocked.
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#7
Have you blown out the burner flu?
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#8
So I increased the distance between the electrode and burner tube and also cleaned the orifice which i have not done in the 10 years i have had the coach. Orifice had debris on it so i soaked it on acetone and blew it off which made a noticeable difference in looking through it plus the fridge runs colder now. So maybe the stuff on the orifice was affecting the air fuel mixture.
Been a couple days and no buildup yet.

Wouldn't the ground wire from the fridge to the battery be a good ground?

Brad
1988 40 ft 8v92 newell
Coach name Big Blue
25 ft Haulmark car hauler with Andersen Anti sway
2012 Toyota FJ Cruiser.
Reply
#9
The ground wire should be sufficient provided it's working properly and on old coaches that is sometimes questionable.

Given your improved results it seems I was probably mistaken about the ground. It seems more likely that excess carbon from the disturbed flame was gathering on the first cooler object it hit and the more it collected the more attractive it was to further collection. There may be more carbon collecting further up in the system so when you have the time and inclination it might be worth checking, though given the improved performance you are getting it's probably not a big urgent problem.

Thanks for sharing what you did and what resulted, that helps us all in the future.
Jon Kabbe
1993 coach 337 with Civic towed
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