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Old 02-21-2016, 01:45 AM   #1
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Fridge won't stay on in LP

I have a '94 Thor Residency Class A, and my Dometic fridge will not stay running in LP. It work like a flawless champ on shore power, or generator power, but not on LP. Fridge will light and stay on anywhere from just a couple of seconds, and sometimes this last summer even lasted a few minutes...but inevitably, it will go into "check" mode and it all done working.

I tried to look and see if there was anything obvious to clean or whatnot, but I'm wondering about any experience with this and what was the problem in your case. I'm leaning to a bad control module or some sort of sensor that's malfunctioning...since it will light sometimes, just never stays lit.

Cheers in advance for the input!

Mike
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Old 02-21-2016, 02:11 AM   #2
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1994......

Look at the control module on the back of the refer. Remove the Black cover. IF the module epoxy is beige/yellow, REPLACE the control board. 1993 thru 1997 Dometic control modules had a intermittent check light failure. There is NO fix for this other than replacing the module. The NEW module will have a green epoxy. IF your module has the green epoxy then the module has been replaced from the original.

If module replaced then flame sensor is not 'proving' flame has lit.
Thermocouple is positioned above flame. It needs to be clean (no soot/carbon build up) and 'engulfed' in flame (heats up sends signal to board----hey flame lit ok to keep gas valve open)



If thermocouple is defective, then it will not keep the flame lit (burner will still light and then go off in about 45 seconds or less)

A common failure is the Spark Plug electrode. It gets old and brittle over the years and/or the white ceramic that houses the metal end has small cracks and bleeds the spark.
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Old 02-21-2016, 09:39 AM   #3
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Try cleaning the burner. Over time they get plugged up with dirt and rust. Compressed air works well. It did for me on my old camper that I had.


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Old 02-21-2016, 11:10 AM   #4
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The Dometic in my '97 Motorhome was doing something very similar. It would light on the gas but only stay lit for a minute or so, however it would work flawlessly on electric. I searched on YouTube for a solution and came across this video. I did what was explained in the video and it fixed the problem. It worked perfectly on gas. I now do a thorough cleaning of the gas components of the refrigerator each spring. I hope this is helpful and Good luck!
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Old 02-21-2016, 07:00 PM   #5
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1994......

Look at the control module on the back of the refer. Remove the Black cover. IF the module epoxy is beige/yellow, REPLACE the control board. 1993 thru 1997 Dometic control modules had a intermittent check light failure. There is NO fix for this other than replacing the module. The NEW module will have a green epoxy. IF your module has the green epoxy then the module has been replaced from the original.

If module replaced then flame sensor is not 'proving' flame has lit.
Thermocouple is positioned above flame. It needs to be clean (no soot/carbon build up) and 'engulfed' in flame (heats up sends signal to board----hey flame lit ok to keep gas valve open)



If thermocouple is defective, then it will not keep the flame lit (burner will still light and then go off in about 45 seconds or less)

A common failure is the Spark Plug electrode. It gets old and brittle over the years and/or the white ceramic that houses the metal end has small cracks and bleeds the spark.
Thanks so much for the input! That's good stuff. If mine is an old module that needs replacing ultimately, any suggestions on where to get it from? Are there any replacement modules that seem to have more success than others? Theres lot of good info you gave me....really appreciate that. Going to go home tomorrow and check out all those things.

Mike
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Old 02-21-2016, 07:02 PM   #6
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Originally Posted by Inthe70s View Post
The Dometic in my '97 Motorhome was doing something very similar. It would light on the gas but only stay lit for a minute or so, however it would work flawlessly on electric. I searched on YouTube for a solution and came across this video. I did what was explained in the video and it fixed the problem. It worked perfectly on gas. I now do a thorough cleaning of the gas components of the refrigerator each spring. I hope this is helpful and Good luck!
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Old 02-21-2016, 07:09 PM   #7
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1994......

Look at the control module on the back of the refer. Remove the Black cover. IF the module epoxy is beige/yellow, REPLACE the control board. 1993 thru 1997 Dometic control modules had a intermittent check light failure. There is NO fix for this other than replacing the module. The NEW module will have a green epoxy. IF your module has the green epoxy then the module has been replaced from the original.

If module replaced then flame sensor is not 'proving' flame has lit.
Thermocouple is positioned above flame. It needs to be clean (no soot/carbon build up) and 'engulfed' in flame (heats up sends signal to board----hey flame lit ok to keep gas valve open)



If thermocouple is defective, then it will not keep the flame lit (burner will still light and then go off in about 45 seconds or less)

A common failure is the Spark Plug electrode. It gets old and brittle over the years and/or the white ceramic that houses the metal end has small cracks and bleeds the spark.
Great pics btw!
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Old 02-21-2016, 11:25 PM   #8
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IF you need to replace the circuit board.......Dinosaur Electronics.
High quality PC ----find which replacement you need and then goggle that board for pricing

http://dinosaurelectronics.com/Dom_boards.htm
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Old 02-21-2016, 11:42 PM   #9
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See the steel tube just protruding from the insulated shroud, which is above the flame in the burner photo. I take a large blade screwdriver and rapidly but lightly tap on the this tube directly. Much rust and scale will then fall, emptying the tube of loose debris. This way when driving there will be less chance of dirt shaking loose from the inside of this tube.
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Old 02-22-2016, 12:02 AM   #10
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See the steel tube just protruding from the insulated shroud, which is above the flame in the burner photo. I take a large blade screwdriver and rapidly but lightly tap on the this tube directly. Much rust and scale will then fall, emptying the tube of loose debris. This way when driving there will be less chance of dirt shaking loose from the inside of this tube.
That is the 'flue' and inside of it is a 'flue baffle' which hangs down from top

The 'flue baffle' should be removed once a year and wire brushed clean. It is spiral in design to evenly distribute the heat from the propane flame.

With it out the flue should also be brushed to remove rust/debris......just like a chimney sweep.

Clean flue/flue baffle makes for better 'cooling' effect and burner slots don't end up with crud falling down/blocking them.

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Old 02-22-2016, 12:27 AM   #11
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That is the 'flue' and inside of it is a 'flue baffle' which hangs down from top

The 'flue baffle' should be removed once a year and wire brushed clean. It is spiral in design to evenly distribute the heat from the propane flame.

With it out the flue should also be brushed to remove rust/debris......just like a chimney sweep.

Clean flue/flue baffle makes for better 'cooling' effect and burner slots don't end up with crud falling down/blocking them.

is that picture right side up? I haven't taken mine apart ever, but plan on checking out all these things tomorrow. I'm hoping that the disassembly is pretty straight forward?
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Old 02-22-2016, 12:28 AM   #12
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IF you need to replace the circuit board.......Dinosaur Electronics.
High quality PC ----find which replacement you need and then goggle that board for pricing

http://dinosaurelectronics.com/Dom_boards.htm
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Old 02-22-2016, 01:27 AM   #13
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is that picture right side up? I haven't taken mine apart ever, but plan on checking out all these things tomorrow. I'm hoping that the disassembly is pretty straight forward?
Yes, the picture is correct, the baffle comes out the top.
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Old 02-22-2016, 02:23 PM   #14
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Eureka!

This group is genius.

Well, I thought I should post a timely update this morning. I got home from work, and after a cup of coffee and some love from the Mrs. and our #3, I went out to see what I cold work out. So I took some pics of what I had when I got it apart:

Before I started:



So I pulled it all apart. Cleaned out the burner tube. Sanded / wire brushed / steel wool'd the igniter, the flame detector, and couldn't figure out how the flue-chimney comes out, so i rapped and tapped on it until rust quit coming out. Here's some of what came out of just the flame tube:



I didn't even touch the control module to see first if this cleaning would indeed be the trick. After I got it all cleaned out, hooked it back up and started it up. This was the first flames initially (but it never quit). I noticed the impure yellow and orange and red in the flame:



But it kept running, and after a couple of minutes it turned to this:







Thanks so very very much for all the input guys. Feels really good to have it working on LP. I like making good old things work again! I'm going to check as well about the control panel -- whether or not its the old style or not, and if it is, I may just order up a new one and keep it in the rig as a spare when mine farts out.

These are the times when forums and knowledge bases like these really shine. Appreciate the input....I ran the fridge on LP for 30 minutes without a hiccup. It's off now, and now I have to figure out my brake master cylinder / reservoir leak and possible replacement!

Thanks so much again guys!! Cheers to all of you!
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