Dometic Suicide??

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ZuniJayne

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Mar 5, 2005
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near Albuquerque, NM
Greetings, all...

The Dometic fridge in my trailer has committed suicide on propane.  It will run fine on AC, which means running the poor little Honda 2000 a lot.

This is a recent DSI model that has always worked great at different altitudes, including up to 9200 ft..  When I start it up on propane, it fires off great for about 30 seconds then quits.  I have cleaned the orifice, thermocoupler, and burner. The flue doesn't seem to be blocked.  I've tried 3 different regulators, so I am not sure that pressure is a problem.

I have checked voltages between main terminal block and the re-ignition module.  All the  numbers seem to come out fine.

Any ideas?????

Thanks!


 

Jim Dick

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Hi Jayne,

If your refer works on AC then the cooling unit is OK. Take the control board to a reputable dealer and have it tested. It might be the problem.

 

Gary RV_Wizard

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I would be suspicious of the thermocouple - if it is not getting/staying hot enough to signal a flame is present, the control board will shut off the gas flow.    The board allows gas to flow for a very short time to give the burner a chance to ignite and heat up. If the thermocouple does not report a flame within a short time (20 seconds?), the gas valve is again closed and (of course) the burner shuts off.  A corroded connection in the wiring from the thermocouple will have the same effect as  adefective thermocouple.  So will a circuit board defect which makes it miss the signal from the thermocouple. 

The thermocouple generates a small voltage when it is hot,  in the 20-30 millivolt range.  You should be able to measure it with a sensitive voltmeter.  See http://www.rvmobile.com/Tech/Trouble/Tcouple.htm  for info on Dometic thermocouple operation.
 

gbic1

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Jul 11, 2005
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How do you determine if it is the thermocouple or the board.  Mine is an old dometic 2 way. It work fine on 110  and on propane it kicks on till the igniter stops  then  it goes out. I bought this camper used and it had been sitting for 8 years before i got it last fall. Just fiilled the propane tank tonight and would like to get this fixed before friday.
 

Gary RV_Wizard

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How do you determine if it is the thermocouple or the board.

I don't know any simple way, but I'm not a trained Rv tech either.  Make sure the wire conections are all clean and that you have adequate 12V power to the circuit board.  After that, I guess you buy a thermocouple and try it.
 

ZuniJayne

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334
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near Albuquerque, NM
Greetings, all!

My thanks to all who replied.  I apologize for not answering sooner.  I thought I had the Forum settings checked so I get an e=mail notification if someone responds.  Either that, or my regular e=mail didn't work.

After I posted the note, I went back after the thermocouple with a friend turning the fridge on from inside so I didn't have to do that, then run outside down steep stairs to take a reading.  It only got up to 11 mV before it shut off the gas.  I ordered a new one for $14.95 plus shipping from a place in WA.  I saw that the thermocouple was really sooty, and cleaned it really well, but that didn't eliminate the problem.  It also seemed to have more ohms resistance than was right.

I know the Dometic boards were nighmares, but I'm hoping that it's just the thermocouple at this point.  If that doesn't do it, looks like I'll get a Dinosaur board. Of course, it's out of warranty.....

The gas hot water heater already quit.  Looks like the gas valve is bad on it.  It's an American Standard, which is not very common.  Of course, AS has ONE rep/tech for the whole continent.  :mad:  No one even answers the phone.


I think this rig knows I want to sell it and is rebelling...... :(

 

ZuniJayne

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near Albuquerque, NM
Karl said:
ZuniJayne,

Just curious - what was the resistance of the thermocouple? It should have been very low; in the area of .5 to 10 ohms maximum, depending on the metals (wires) used.

Karl,

The resistance reading was MUCH higher than that.  The new thermocouple came in , and I'll install it tomorrow.  If it doesn't work, then a new "Dinosaur" board it is.....
 

Karl

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How much higher was it? A thermocouple can be made from any 2 dissimilar metals but Chromel/Alumel, Iron/Constantan, and platinum/platinum with Rhodium (10 or 14%) are the most commonly used. You could twist a copper wire and an aluminum wire together at the ends and it would be a thermocouple.
 

ZuniJayne

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near Albuquerque, NM
Karl,

I don't remember the exact number of ohms resistance right now, but the kicker was this.....the igniter ignited, the flame came on, but after about 30 seconds the thermocouple only got up to 11 mV.

I got a new one for $14.95 plus shipping from rvmobile in Everett WA.  Fridge now works like a champ!

 

ZuniJayne

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Mar 5, 2005
Posts
334
Location
near Albuquerque, NM
Gary,

Just found your "kudos" message today, Aug 16.  I wasn't trying to ignore you.

The cell phone you gave me is still doing a great job, and getting good signals in areas that newer models can't.

 
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