Usual disclaimer
I am not a Gas Fitter, I do not play around with LPG, and I have not posted to start a flame war

Can someone shed a bit of light on a Dometic RM 7401 three way fridge problem

History is around March (7 months ago), prior to crossing the Nullarbor from east to west, I must have purchased a bad bottle of gas somewhere
The fridge stopped working on gas, and I noticed the flame on the gas stove became very low

Removing the gas regulator, when I returned home, I noticed a mustard coloured fluid inside one of the pigtails
Setting up a manometer using compressed air, the regulator was only giving less than 5 inches of water pressure
A new regulator and pigtails cured this problem

Returning home this month from a second trip, September (so not hot weather), once again the fridge failed on gas, while coming across the Nullarbor from east to west

It works on 240 VAC
It will hold its own on 12 VDC
Both the stove and gas hot water heater are working OK
The regulator does still have 11 inches of water pressure
Using an inspection camera shows a blue flame, and a clean boiler chimney

It is booked in for a service but there was a two week wait

My theory is that the thermostat has failed or is blocked enough to slow the flow of gas to the boiler
The picture below shows what I think is the gas thermostat, as it has the gas lines going in from the bottles, and out to the flame
I notice what looks like two insulated (I assume live) and one bare end (I assume is an earth) wires

Can someone shed a light, how the thermostat works, and how should I check the wires with my multimeter, so that I can eliminate the switch/circuit board, which I will not be able to access without removing the fridge, as they are situated on top of the fridge

Any help/guidance will be appreciated

 Edit to make the picture a bit clearer

Hello Warren

New pigtail rubber hoses came with new regulator about 7 months ago

I have the normal 11 inches of water pressure after the regulator, which is after the pigtail hoses

I have had an inspection camera looking at the flame which appears blue
I am confident that the jet is OK

Without knowing how the gas thermostat works, I will not touch it
Just in case there are delicate parts in the main board, and I blow something while playing around

Below is a picture of this model fridge (for sale on Gumtree somewhere)
The electric part of the thermostat is the dial on the right
I would have to remove the fridge to access this part

Thanks for trying to help

macka17 wrote:

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The smaller fridges just normally slide out
after removing the screws holding covering boards round perimeter

I've replaced a few 12 elements over the yrs..(top right)

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 Not sure exactly exactly what you mean Macca

Are you talking about the part, on the top right, of the top of the fridge, if so what is in there
The parts list I looked at, has it down as a electronic control box

If you are talking about the 12 volt heating element (attached to the boiler), at the rear, top right of the fridge, then I think that it is OK and working

This particular model has the holding screws going through the sides of the fridge
The vehicle is a Jayco build, and does not have a front fascia around the perimeter

Appreciate your input

Gas fridges should not be used while running on the road. The consequences of refuelling at a servo near where another vehicle is being refuelled with gas there is always the problem of a small gas cloud when an inefficient refueller removes the connection from his vehicle.The gas is heavier than air and will waft along at low level and you have a pilot light on. It will happen one day. Years ago when fridges were only 2 way I used to travel with the gas on. These days too risky. Hope you get your fridge sorted out with the gas problem. Use nice heavy wire direct from the battery ,a fuse and an Anderson plug and your fridge will be colder than running it on gas and you and others will be much safer. Cheers.

patrol03 wrote:

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Gas fridges should not be used while running on the road. The consequences of refuelling at a servo near where another vehicle is being refuelled with gas there is always the problem of a small gas cloud when an inefficient refueller removes the connection from his vehicle.The gas is heavier than air and will waft along at low level and you have a pilot light on. It will happen one day. Years ago when fridges were only 2 way I used to travel with the gas on. These days too risky. Hope you get your fridge sorted out with the gas problem. Use nice heavy wire direct from the battery ,a fuse and an Anderson plug and your fridge will be colder than running it on gas and you and others will be much safer. Cheers.

-- Edited by patrol03 on Tuesday 26th of September 2017 06:25:59 PM

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 Agree with you patrol03

I do not run with the gas bottle switched on, and the fridge seems to work OK on 12 volt

The fridge is in a Jayco motorhome, and I am the first to admit that the 12 volt wires are, much too small
Unfortunately for me, Jayco do not know where the wires go, once they are behind the built in walls/furniture

Jayco could not sell me a wiring diagram, they looked for one for me, on their computer
Their official (Western Australia) stance is, that because there are so many different models, they would have to make a wiring diagram for each separate model

Appreciate your input

Desert Dweller wrote:

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We have a Dometic 3 way fridge in our caravan bought new 5 years ago. It's a different model to yours but they're pretty much all the same except for sizes.

Ours has stopped working on gas twice & 240V once over the 5 years. We got ours fixed by a gas fitter in Yeppoon when we were up north a few months ago, cost us $70 cash in hand.

He cleared a blocked jet & re-aligned the flame which was out of alignment. Works very well now. He said that even just changing gas bottles can cause a blockage if a small particle gets loose in the system.

On the two other occasions that it broke down we had it repaired & serviced by a caravan refrigeration specialist in Melbourne. We could of bought a new fridge with the money they charged.

Good luck with yours.

---

 It is already booked in for a service, so I will wait to see what the problem is/was

There are apparently not many spare parts in my part of the country

They will do a service ($140), and then tell me what parts are required

I believe that one difference between the 3 way fridges, is that my size, about 100 litres, only have a "SN" or "N" rating (Sub Normal, or Normal)
They are only good up to about 32°C ambient temperature

It appears that larger gas fridges have a "T" or Tropical rating, which I can not fit in to my motorhome, but those larger fridges are good for up to about 42°C ambient temperature

I appreciate your feedback Desert Dweller

Tony Bev wrote:

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Desert Dweller wrote:

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We have a Dometic 3 way fridge in our caravan bought new 5 years ago. It's a different model to yours but they're pretty much all the same except for sizes.

Ours has stopped working on gas twice & 240V once over the 5 years. We got ours fixed by a gas fitter in Yeppoon when we were up north a few months ago, cost us $70 cash in hand.

He cleared a blocked jet & re-aligned the flame which was out of alignment. Works very well now. He said that even just changing gas bottles can cause a blockage if a small particle gets loose in the system.

On the two other occasions that it broke down we had it repaired & serviced by a caravan refrigeration specialist in Melbourne. We could of bought a new fridge with the money they charged.

Good luck with yours.

---

 It is already booked in for a service, so I will wait to see what the problem is/was

There are apparently not many spare parts in my part of the country

They will do a service ($140), and then tell me what parts are required

I believe that one difference between the 3 way fridges, is that my size, about 100 litres, only have a "SN" or "N" rating (Sub Normal, or Normal)
They are only good up to about 32°C ambient temperature

It appears that larger gas fridges have a "T" or Tropical rating, which I can not fit in to my motorhome, but those larger fridges are good for up to about 42°C ambient temperature

I appreciate your feedback Desert Dweller

---

That makes sense to us. Ours struggles when the temperature hits 30 degrees when its on gas. Time to head for a caravan park, it copes OK on 240V.

Forgot to say that we had an extraction fan fitted & sail track fitted for 90% shade cloth over the side that the fridge is on. Ours is the Dometic 90L.

The freezer section copes no matter what temperature it is but in the past the fridge section has failed us quite a few times & we've had to ditch food. The new measures have helped a bit.  

PeterInSa wrote:

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Re (My theory is that the thermostat has failed )

I do not know if the Thermo. controls the temp on 240Vac.

We had problem with a different frig to yours when on Gas. Probably a grand child had played with the Thermo knob and you could turn it, but nothing would happen the shaft had been broken. Could be your problem.

Peter

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 From what I can make out, my temperature dial, goes to an electronic type box, which in turn controls both the 240 volt heating element, and the gas burner

The common pieces of both the 240 volt and the gas system are, the temperature dial, the temperature probe inside the fridge, and the electronic control box, (called Electronic Complete, in the parts section)

The 240 volt seems OK, this tells me (but I could be wrong, as I am not a Gas Fitter), that the problem lies in the, (what the part list calls the) Gas Valve

I call this Gas Valve the thermostat, as it has the gas line from the gas bottle regulator going in, and the gas line to the gas burner, going out, and therefore must somehow adjust the gas to adjust the temperature

I am only guessing about what the problem is

Thanks for your input Peter, it is appreciated

A bit of an update

I had the gas side of the fridge serviced yesterday
Unfortunately when I picked the vehicle up, I only talked to the salesman, and not the Gas Fitter
He could only quote what was written on the invoice, which is as follows

Service Gas side of fridge. Clean ignition point
Cleaned out Gas lines
Check pigtails
Check regulator for correct pressure
Re-tested, all appears to be working correctly while in the workshop

I will assume that, "Cleaned out Gas lines", means, that there may have been something in the gas lines

Since I last tried to use the fridge on gas, I have purchased a wireless thermometer, with three stations
Below are the temperatures I now have, with the fridge set at around the three quarter setting, (I do not have numbers on my dial)
The fridge is empty, left open for a few hours to give me a ballpark temperature to start from, there is one beaker of water in the freezer, and the fridge door will not be opened during this test

At the 17 hour mark, I noticed that the freezer, and fridge had started to warm up
From then on it was an hourly check, (no drama as the wireless thermometer works from inside the house)

Just after the 24 hour reading, I went to see what I could see, which was nothing
The flame was about the same as when the test was started, but the condenser was not as warm

I tried to see if there was any 12 volt power to the "GAS VALVE", none on the right side, but perhaps the rust of the positive connection was stopping the multi-meter probe from making a reading
I could not get the probe to the left hand connection
I gave the "GAS VALVE" a tap just in case something had stuck. (it may be a coincidence but at the 26 hour reading, the temperature in the freezer started to drop, but so did the ambient temperature

Still guessing that the "GAS VALVE" or what I would call the gas thermostat is the problem
I shall keep checking the temperatures on gas as the temperature of the freezer has definitely started falling

Later on in a few days, I shall do the same test on 240 volt

Hoping that one of the techies can give me a clue, and will appreciate any guidelines

Tony Bev wrote:

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<, I have purchased a wireless thermometer, with three stations

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Bill B wrote:

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Tony Bev wrote:

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<, I have purchased a wireless thermometer, with three stations

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Tony, can you provide a link to this please ?

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 Here we are Bill

My local Jaycar, (I assume all Jaycar shops)

The Wireless LCD Thermometer and Hygrometer model XC-0322 comes with one Thermometer Sensor in the package

Here is the link to the above

You then have to buy another two sensors model XC-0324 which are on the shelf close by

Here is a link to the above sensors

I also brought two Jiffy Boxes to put the fridge/freezer sensors in, so that they would not be damaged, when I am on the road
Jiffy box size 83x54x31mm, (the smallest I could use), I cut the 8 reinforcement bars out of the two long sides, to make the sensors fit
Not sure if you would need the jiffy boxes, but they only cost about $2.50 each

Also the main thermometer has its own temperature reading
If you only want to read the fridge and freezer temperatures, from inside your Tug/RV/House/Awning, then you would only need one extra sensor

Hope that this info is useful to yourself and others
It is certainly giving me an insight of what my three way fridge is doing

Wanderlust wrote:

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Looking forward to a resolution here as I have the same fridge, although it is currently working OK but you never know.
My thoughts - Is the piezo ignition active? Could some of that mustard coloured liquid have run through to the new jet and clogged it?
Good luck.

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 That was one of my theories, about the mustard coloured stuff

But...
I explained about the mustard coloured stuff to the saleslady, and have no idea what message was passed onto the Gas Fitter

From the gas bottles to the fridge, the gas line goes under two chassis rails, leaving two "U" loops
I will assume that if the gas line was cleaned out, at the service, then the mustard coloured stuff, which may have been sitting in the "U" loops, is no longer there

The piezo ignition has always worked, as I could always feel the heat of the flame at the exhaust pipe in the vent

I appreciate your input, Andy

Edited to say that at the 39th hour the temperatures are
Freezer minus 19.1°C
Fridge 4°C
Ambient temperature in motorhome 12.1°C

Sorry for late answer Tony\Bev.

Yes. That point. element under. was around $125 from memory.

I've only had Roadstar for last 25ish yrs. (b4 this little Coromal)

Their 3 ways were held back behind sid covering boards.

Unscrew covers Slide it out.

Repair. push back. Simple.

The Waeco Compressor units slid straight into place too. 

Covering strips rescrewed.

--------------- 

If people buying new motorhomes or needing a fridge.

Repair
eplace\ update,whatever

I don'r know why they don't just install a Compressor unit.
More efficient under wider temp ranges.
and seeing as most carry Solar. (Or should be)
They run themselves.

NEVER need to touch them. ANYWHERE.

Same pricing for equiv sizes too (or were)
Factory seconds avail, as are second hand.

Those 3 way are soooo obsolete nowadays.
Just like those "Caravan" Air cond's.

NOO gas leaks. Blockages of gunk.

NOO Not getting down to, or holding temp's on 12v.

NOO needing 240 to get them down to anywhere decent.

Some people should think about them. seriously.

macka17 wrote:

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Sorry for late answer Tony\Bev.

 

Yes. That point. element under. was around $125 from memory.

 

I've only had Roadstar for last 25ish yrs. (b4 this little Coromal)

Their 3 ways were held back behind sid covering boards.

Unscrew covers Slide it out.

Repair. push back. Simple.

 

The Waeco Compressor units slid straight into place too. 

Covering strips rescrewed.

 

--------------- 

If people buying new motorhomes or needing a fridge.

Repair
eplace\ update,whatever

I don'r know why they don't just install a Compressor unit.
More efficient under wider temp ranges.
and seeing as most carry Solar. (Or should be)
They run themselves.

NEVER need to touch them. ANYWHERE.

Same pricing for equiv sizes too (or were)
Factory seconds avail, as are second hand.

Those 3 way are soooo obsolete nowadays.
Just like those "Caravan" Air cond's.

NOO gas leaks. Blockages of gunk.

NOO Not getting down to, or holding temp's on 12v.

NOO needing 240 to get them down to anywhere decent.

Some people should think about them. seriously.

-- Edited by macka17 on Thursday 5th of October 2017 10:02:30 PM

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Thanks for your input Macca

Yes. That point. element under. was around $125 from memory.

It is definitely not an electrical heating element at the boiler that is the problem, as they are not used when operating on gas
If you are talking about an element on top of the fridge
It is called (I think), an electronic control complete, and they are about $460

Repair
eplace\ update,whatever

I don'r know why they don't just install a Compressor unit.

That is plan "B" if/when I throw the towel in, on this 3 way fridge
Strangely enough I have found, that not all 12 volt upright compressor fridges, are "T" rated

I feel for you, rodden
At least I have a bit of battery and solar, to give me some options
Like yourself, I do not have the room to put a larger fridge in my motorhome

I shall certainly advise if I am able to repair mine, and would be over the moon if I could change it into a "T" rated fridge

I am still experimenting by looking at the temperature numbers, with the fridge on gas
Later on I shall run the fridge on 240 volt and by comparing the numbers, I hope that I can eliminate some faulty part/s

There are a lot of temperatures numbers (on the net), of what different rated three way fridges will perform in

I have sent the following email form to Dometic Australia, hoping to get some numbers, direct from the horses mouth

Dear Sir/Madam
Sorry about no phone, (I have given a wrong number), as my wife does not like me giving it out, due to previous unsolicited calls
I have a RM 7401 fridge, it is "SN" rated.
Can you advise if you make a three way fridge of the same size, which is "T" rated.
Also could you tell me what maximum ambient temperatures your "SN", "N", "ST", and "T" rated three way fridges will be able to perform in

Thanking you in advance for an answer, as depending on what type of fridge I purchase, will dictate, my future travel destinations
Thank you 

Their answer so far

Thank you for taking the time to complete the form.

Kind Regards

Dometic Australia

It is early days for me, as I do not have any road trips planned until the end of the month, and I now have a small compressor chest fridge, as backup

I now give up and throw the towel in, in regards to this fridge
It was not for lack of trying
After much research I find that there are five main parts which could go wrong, which may be of interest to others

1. "Absorber," (sealed unit) the part which holds the refrigerant mediums (for use of a better word) gasses, seems to be OK, as there was no visible leak. Unable to find a price in Australia
   
   
2. "Electronics Complete," the electrics on top of the fridge which sends the signals to the 12 volt, 240 volt and reigniter, seems to be OK. Approximately $460 plus freight
   
   
3. "Reigniter," the part which sends the signal to the gas valve, and piezo, then receives the signal from the piezo, when the flame is burning, seems to be OK. Approximately $190 plus freight
   
   
4. "Gas Valve," which allows and shuts down the gas to the burner, appears to be OK. Approximately $230 plus freight
   
   
5. "Gas Burner," where the flame is, which can stop some of the gas flame, appears to be OK. In my local area it was $140 for the fridge service, and the invoice says that the fridge was working in their workshop

The fridge works as it should until the ambient temperature gets above about 30°C and from that point on, it is just not reliable

I removed the fridge, very difficult as either the wood has swelled, or the fridge sides had buckled, since it was installed
I had plans to turn it upside down etc, but I would have first had to remove the electrics on top of the fridge, as my hands are a bit on the clumsy side, I gave this idea a miss

I have ordered a 12 volt upright fridge, with a climate class of T+, supposed to be good for 43°C

I am not knocking this three way fridge, because my brother has the same type, made in 2012, which appears to work OK, while mine was probably made in 2006

All I can say in layman speak, is that I could not find any visible fault with any of the parts mentioned above

As my final post on this particular thread

I had fitted an EVERCOOL Platinum 110 Litre 12/24 Volt Fridge

It has lived up to its advertised promise of being a climate "T plus" rating of good for up to 46 C

In January 2018 at Kimba SA, it was 43 C out side, and over 46 C inside the motorhome, and with the fridge set at 2 C, the beer was cold

The boss is rapt with the fridge, as we never threw any food away

In the spirit of EXplaining, and not COMplaining, here is what I thought could be the downside of this fridge

• In a normal day of around up to 36 C, it cycled approximately 50% on and 50% off, in daylight hours
  I have no way of knowing what happened in the hours I was asleep
  But... at 43 outside ambient temperature it seemed to be cycling about 85% on, and 15% off in the hours I was awake
• You can not fit 2 litre bottles of milk in the fridge door, so you will have to get to using 1 litre bottles
• Using wireless temperature guages, I found cold spots in the fridge
  With the top shelf of the door running at 2 C, the back wall of the frige was showing minus 2 C
  This meant that sometimes the butter was a bit hard, but by crikey the beer was cold

KMMA wrote:

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Tony,
Do the compressor frigs also get rated like the 3 Way Friges eg T, S, SN ect ?

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 Yes, KMMA

Compressor fridges are climate rated the same as a three way fridge

They are rated on their ability to keep the inside of the fridge cool, while the outside is a certain temperature

Do not quote me on this as I am only going from memory

"S" rating means that the fridge will work OK up to about 28ºC
"N" rating means that the fridge will work OK up to about 34ºC
"T" rating means that the fridge will work OK up to about 42ºC

My EvaKool fridge has a rating of "T+" (Tee plus) which is better than "T" rating

Beware that I have seen el cheapo 12 volt compressor fridges on Gumtree, and EBay with a climate rating of "S and N and T" rating
I am not sure what this means, (having three different ratings for the same fridge), and I therefore assume that the sellers, do not know what it means

Hope that this info is helpful to you

Yippee our 12v has a "T" rating. Thanks for that info Tony, now this is my final comment on this thread