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tri5ron's avatar
tri5ron
Explorer
Jan 10, 2018

Dometic RM2852 fridge wont stay lit ?

Hello All,
It's been a LOOOooonnnnggg time since I've been around here, but Open Roads Forum has always been my "Go-To" place when I need to get knowledgeable experienced advise... so here I am.

I now live in a senior citizens community, and I "hang out" at the RV Storage Lot here within the community. Being that many of the citizens here are on limited incomes, and/or not able to do all of their own maintenance on their rigs, I am often asked to help them out.

I do have some past experience with RV fridges not working properly, and I have a (very basic ) knowledge of both their function and common problems. I have had to replace the circuit board on a couple of rigs over the years, using the "Dinosaur Brand" purchased from Randy at BestConverter.com. These worked quite well for those repairs.

Ok, so here's what I have so far.

The senior citizen owner of this fridge, Dometic RM2852, tells me it would not self light when switched to propane... but he could get it to light using a long BBQ lighter.
It would stay lit for several hours, but at some point it would shut off and the "check" light on the control panel would then come on.
I have verified that this is what happens.
First I went to check for carbon build up at the igniter and did find some carbon there causing a weak spark.
I removed the build up,... shut off the fridge,... turned it back on,... and it lit at first spark. YAY ! I thought I was "out of the woods" that easy, but unfortunately, that does not seem to be the case.

When it did light, it ran for several hours, (overnight actually), and yes it did get plenty cold inside the fridge. All seemed well, but then at some point it will shut itself off and not re-light. (no self sparking from the igniter). "check" light comes on and stays on.

The propane tank is full, and yes I have fully checked and verified there is no spider webs of other blockages in the gas/air tube.
When is WAS burning,... I was getting a nice clean Blue flame. no problems there.
It just decides at some point to shut itself off.
We at at sea level, and there has not been any wind blowing it out. so it's not that either.

I called Randy, and He does not think it is the circuit board,... I also just got off the phone with Dometic Customer Service. I spoke with a nice lady there "Nina", who also thinks it is not the circuit board.
Nina checked with somebody else there, (I'm assuming another service technician), who also does not think it is the circuit board.
They suggested a possible DC 12v signal problem going TO the circuit board,... and suggested that I check, clean, and re-apply Dielectric grease to all connections in the electrical system supplying the fridge.
I have done this to all the connections on the board itself,... but not beyond that yet. But to be honest,... I'm fairly confident there is not an issue with electrical power supply going TO the fridge.

Nina also suggested the possibility of it being,(this is a quote), "the electrical component with the porcelain insulator".
I asked her if she meant the "Thermal coupler", and she replied "No,...that model fridge does not have a Thermal sensor".

That does not sound correct to me,
but maybe it is ? ? ?,... I dunno.

SOOoooo,... I figured I'd "Go running home to Momma", (i.e.- come to all you knowledgeable folks with my questions.

I'm trying to help out a friend here, and hopefully avoid having him go spend $$$ needlessly. He lives a Very modest life on a VERY limited income. He does not have the luxury of just taking it to a RV Dealership every time there is a glitch in his giddy-up.

So what say all of you ?
What do you think would be causing this periodic shut down when running on propane ?
What would you check next ?

I have not yet checked "the porcelain insulated electrical component",... but I still think that is the thermo-couple which tells the controller "Yep, the flame is still lit".
Maybe I'm wrong there,... but if it IS the thermo-couple,.. and the fridge DOES run for several hours before shutting itself off,... then doesn't it stand to reason that the thermo-couple is still operating properly ?

Any advise and replies are greatly appreciated.
Thanks for taking the time to read this long post.
Cheers,
Ron
  • tri5ron wrote:
    Thanks for all this info so far. You guys are great.
    The product number for this fridge is
    921146004.

    I probably won't get back to the fridge until tommrow or over the weekend.


    Then it has a thermocouple for flame sensing AND a spark electrode for ignition

    Thermocouple has to sense the flame lit otherwise the circuit board shuts down DC to Gas Solenoid so raw fuel doesn't accumulate in burner area

    Thermocouple tip MST be engulfed in flame when it lights off
    Thermocouple MUST be clean...no soot/carbon build up
    Thermocouple MUST have a clean/tight connection
    Thermocouple should produce 25-35 Millivolts to lower board when heated (Lower then 18 millivolts will cause erratic flame operation)
  • Thanks for all this info so far. You guys are great.
    The product number for this fridge is
    921146004.

    I probably won't get back to the fridge until tommrow or over the weekend.
  • Lots of valid opinions but do yourself a favor. If you are hellbent on repairing it yourself, find the service manuals for the particular model and follow the troubleshooting matrix to the letter. That will probably save you a few bucks instead of guessing and throwing parts at it. You may run into a roadblock or two, most people don't own board testers etc, but there are workarounds that can be found online.
  • thank you for all the replies so far.
    I will check and verify all the suggestions and I will report back with my findings and the product number.
  • Depending on product number whether fridge uses a thermocouple and electrode OR just a 'spark electrode'

    Both are types of sensors but depends on design of circuit board
    Thermocouple heats up...internal expands making up circuit (electrode would just be means of high voltage spark)

    Later production models only used a spark electrode for spark and flame sensor
    Spark Electrode uses a signal generated by the flame----rectification (ionization)
    This milliamp signal returns to circuit board via the spark electrode to prove flame lit
    IF spark electrode connections/terminals are dirty/corroded.....no milliamp return signal
    If spark electrode is dirty/carboned up......no milliamp return signal
    If spark electrode ceramic insulator is cracked,,,,,,milliamp return signal goes to ground---no return to circuit board


    Product numbers with both thermocouple and spark electrode
    Up to 921146154

    Product numbers with JUST spark electrode
    921146167 and later
  • Two items could be an issue.
    The ignitorprobe could be bad along with it's high voltage wire. This would stop the refer fromlighting and then shut down because the flame sensor didn't see flame.
    Next would be the thermo couple. If not directly in flame or the burner is covered with debris from the stack.
    Start by cleaning the burner area. Clean the thermo couple with steel wool.
    Inspect the porcelain electrode for any cracks. inspect the high voltage lead for any nicks abrasions in insulation.
  • Nina could be right. I just replace the board on mine and then found that the wire running through the ceramic insulator had come loose from the sensor. It was working just the way you described and wouldn't re-ignite reliably. Fortunately, its not that expensive, and luckily, there was one available in Canada from Dometic!
  • When it quits start checking DC voltage. My guess you will find none. Possibly the thermister, the little bulb attached to the right hand fin inside the box. If that does not signal warmth the refer will not restart to cool the box.

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