Dometic fridge RM 7361; problem on gas

[michaelconroy]

Hi

My Dometic fridge RM7361 has a 3 way operation. On 230v & 12v it works fine. On gas it does not chill at all. The gas bottle is full & the gas is flowing (checked rings on hob). The gas ignites and there is a flame at the gas jet and the top vent gives off warm air. Any suggestions please? Mike

[StuartO]

Working on 12v and 240v involves an electrical heating collar around the same evaporator stack (or whatever they call it) that the gas flame heats, so on the face of it if your fridge has a gas flame and you can feel warm air at the outlet, your fridge should be working on gas as well.

 

So maybe the gas flame is not aligned properly or the chimney is a bit blocked up?  Maybe worth trying to brush any cobwebs etc out of the chimney above where the gas flame burns using a bottle brush.

 

[Robbo]

I would suggest the first thing to check is the gas jet just prior to the burner unit.

 

The jet may be partially blocked causing your fridge to work inefficiently. Remove the jet and blow it out with compressed air - don't be tempted to poke it with anything. Or buy a new jet.

[michaelconroy]

Thank you. I'll try that. M

[michaelconroy]

Thanks for the advice.

 

I did as you both suggested. I couldn't find a way to clean the chimney apart from blowing down it (with the jet removed) and it did appear to be clear.

 

I removed the jet assembly and its feeder pipe. I think there was a small blockage in the jet which I managed to remove by blowing through it.

 

On re-assembly the gas flame looks a lot bigger and healthier and, after 12 hours, the fridge is definitely cooler although the ice tray in the freezer compartment has not frozen. That said the ambient air temperature was 37° yesterday.

 

Three questions.

 

1. Would it be best to get the fridge to temperature by using 230v then to maintain that temperature with the gas?

 

2. Despite the gas being ignited the indicator light on the front of the fridge is flickering slightly (not as vigorously as it does when there is no flame). Is that normal or a sign of a problem?

 

3. What does it mean to say that "the flame may not be aligned correctly"? How should it be aligned?

 

Thanks again.

 

Mike

 

 

 

[StuartO]

I was referring to the position of the burner under the chimney and unless it has been displaced (eg bent bracket) it should be OK.

 

It sounds like you are now up and running, although it might be worth replacing the burner jet, to ensure it is 100%; your burner has after all done a lot of work over the years and cleaning burner jets is not easy or reliable.  They are available and not that expensive.

 

We put the fridge on 24 hours before we depart on a trip to get it down to temperature and in very hot weather I wouldn't be surprised if it took a while to cool down.  If you can use 240v during this pre-departure period then it will save gas and might be a bit more efficient - although remember that whichever energy form you use to drive the fridge, an adsorption fridge works by heating up the evaporator unit, so there shouldn't be much difference.

 

[michaelconroy]

Thank you StuartO.

[Clive]

To clean the flue you need to remove both top and bottom grille vents. Then through the top grill vent remove one small screw to enable the top angled pipe to be lifted off the top of the flue. You will then see a little bit of wire, lift this up and it will pull out a twisted stainless steel plate than hangs inside the flue pipe. This is there to cause the heated gasses to swirl and impart their heat to the outer tubing. Carefully clean this blade and the tube with a pipe cleaner. Now going in below undo small screws to remove the guard around the burner unit. Clean all around and vacuum away all soot and dirt.

Remove the small jet and blow through it then look through it to confirm it is clear. DO NOT POKE ANYTHING INTO THIS JET as it will make the hole bigger, the fridge will use excessive amounts of gas, it will soot up very quickly and could cause carbon monoxide to be produced that could kill you.

Reasemble in the reverse order and test.

Or look up your local Dometic Service partner on the Dometic web site and get them to do it as it is not a job for an amateur.

http://www.dometic.co.uk/service/service-partner-network/

 

Hope that helps

 

[Casimir]

I have had a similar a problem with my Dometic fridge (RM7655). The fridge was not performing properly on gas whilst touring in Spain over a four week period in July and August with high temperatures every day. We mostly staying on aires and without EHU. The gas burner appeared to be working properly but on my return I removed and cleaned it anyway. I then discovered a significant amount of soot in the flue. I managed to dislodge the soot with a semi-flexible cable. I then vacuumed the flue with a small flexible tube as best I could. The top vent on my van is in the roof rather than on the side so I have not been able to access the angled pipe and steel plate at the top of the flue.

I also fitted a Brunner/Vento 12v fan to help with ventilation as recommended on this forum and elsewhere, as most of our travels are in Spain, France and Portugal.

I understand that if the van is not reasonably level this can also cause poor fridge performance. Does anybody know if this is true or not?

Whilst I have not used the van for a couple of weeks or so, initial tests suggest that soot in the flue was responsible for the poor performance of the fridge.

[Derek Uzzell]

Casimir - 2016-09-02 11:40 AM

 

...I understand that if the van is not reasonably level this can also cause poor fridge performance. Does anybody know if this is true or not? /

 

Depends what you mean by “reasonably level”.

 

A 7-Series Dometic fridge is designed to be ‘tilt tolerant’ up to 6 degrees of tilt (I think you’ll find that guidance in your fridge’s manual) which is tiltier than most people would be prepared to live with in a parked-up motorhome.

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/How-leaval-must-a-gas-fridge-be-when-running-on-gas-/27498/

[Casimir]

Derek, thank you for your helpful information about tilt toleration.

Unfortunately the guidance in my 7-Series manual is less than helpful and suggests checking that  "The refrigerator is not tilted excessively".

[Geoff Cole]

HI,

I thought a brief explanation might help in understanding how these fridges work.

There are 4 main components:

1, the generator, this is where the mixture of Ammonia and water is heated up

2, the condenser, this is where the Ammonia gas is condensed into a liquid

3, the Evaporator, this is where the cooling takes place as the Ammonia evaporates causing cooling

4, The Absorber, This is where the evaporated Ammonia is absorbed back into the water.

 

The above is very simplistic I have left out the complex technical details to save boring you all to death,

 

The heating takes place in the generator by either electric elements or a gas jet. There are not normally any problems with the electric elements they either work or fail. The gas jet and flue needs more care, as debris can form to block the jet and should be cleaned as should the flue annually if the fridge is used regularly on gas.

There are no moving parts in the system to go wrong and in the event of a leak these systems cannot be re-gassed as they use a mixture of Ammonia, water and Hydrogen in very precise quantities.

If the system stops working and there is no fault in the heating of the generator then there is either a leak due to damage, or corrosion within the system causing a partial or blockage within the pipe work which is made from steel. The system does contain corrosion inhibitors, but corrosion can still take place over time.

When operating in hot weather, extra cooling of the condenser by using a fan can greatly assist the efficiency of the fridge also keeping a couple of freezer packs in the freezer compartment will help.

Partial cooling on gas is usually caused by debris on or around gas jet, excess soot in flue or gas bottle running out.

 

Hope this littleexpanation is usefull

Regards Geoff C

[747]

There may be a clue in the fact that the OP said the ambient temperature was 37 degrees. Many owners find their fridge does not perform well at that temperature.

 

It can help slightly by having the van positioned with the Fridge vents on the 'shady' side of the van and even temporarily removing the vents in those conditions.

 

Another method is to fit a Fan (or two) behind the top vent to expel warm air to the outside and promote a ventilating draught.

[michaelconroy]

Hi all

 

I thought I had sorted the problem by cleaning out the gas jet etc. The gas lights quickly but is only at a low level, despite the temperature setting on the dial on the front of the fridge.

 

I had a spare gas jet and fitted it, also cleaned out the burner. Still the gas lights with no delay but doesn't respond in any way to the temperature dial on the front of the fridge.

 

I then thought it might be a fault in the gas valve until I started to think about the temperature dial, the fact that it offers no resistance.

 

So I opened up the Electronic Component Assembly (pcb) and found that the temperature shaft offers no resistance because it's is not attached. It doesn't look as though it's broken off, though, both the end of the shaft and the component are smooth.

 

What am I missing here? Is the shaft meant to fit in the pcb, or what?

 

Do I need to buy a new pcb & a new shaft?

 

Finally (2nd image), on removing the pcb an unattached cable was revealed. I can find no connection for it anywhere. Is it a standard but redundant cable?

 

[Derek Uzzell]

Logically the ‘temperature shaft’ must connect to the pcb. Even though the inner end of the shaft in your photo is smooth, and the ‘component’ in the pcb is also smooth, it must be assumed that the shaft has broken and the ‘component' (the smooth circular grey piece of plastic in the pcb) is part of the broken shaft. (Perhaps, when attempting to regulate the temperature, repeatedly twirling the control-knob has worn both broken ends smooth?)

 

This link carries spare-part diagrams for an RM7631 fridge

 

http://www.leisurespares.co.uk/files/rm7361.pdf

 

and the part identified as 487C (SHAFT TEMPERATURE) on Page 1.7.3 suggests that the shaft is a separate part that is inserted into the pcb. If it were me, I’d carefully drill a small hole in the centre of the ‘component’ in the pcb, carefully insert a thin screw into that hole and then pull on the screw to try to extract the broken-off end. If that didn’t work I’d check that ‘resistance’ could be felt when the screw was rotated clockwise and anti-clockwise (and that this had an effect on the gas flame) and if both of those things happened I’d then pin the two broken parts of the shaft together. But if you can extract the ‘component’ from the pcb and fit a complete new shaft, that would be best.

 

Dunno about the unattached cable - perhaps there is an AES version of this fridge that the cable applies to and (as you’ve suggested) it is redundant on the non-AES model.

[Keithl]

Michael,

 

I can confirm without doubt that the shaft is broken!

 

There is a very small 'D' shaped section left in the variable resistor which you will have to remove. When I replaced ours 6 or 7 years ago I did exactly as Derek has suggested, ie drilled a very small hole in it and used a tiny self tapping screw to get a purchase and pull it out.

 

I posted with pic's of the old and new part so a search may throw up my old post.

 

Keith.

[BKen1]

michaelconroy - 2017-09-26 1:21 PM

 

Hi all

 

I thought I had sorted the problem by cleaning out the gas jet etc. The gas lights quickly but is only at a low level, despite the temperature setting on the dial on the front of the fridge.

 

I had a spare gas jet and fitted it, also cleaned out the burner. Still the gas lights with no delay but doesn't respond in any way to the temperature dial on the front of the fridge.

 

I then thought it might be a fault in the gas valve until I started to think about the temperature dial, the fact that it offers no resistance.

 

So I opened up the Electronic Component Assembly (pcb) and found that the temperature shaft offers no resistance because it's is not attached. It doesn't look as though it's broken off, though, both the end of the shaft and the component are smooth.

 

What am I missing here? Is the shaft meant to fit in the pcb, or what?

 

Do I need to buy a new pcb & a new shaft?

 

Finally (2nd image), on removing the pcb an unattached cable was revealed. I can find no connection for it anywhere. Is it a standard but redundant cable?

 

Had the same problem a few years back and repaired the spindle ,,,,,did a YouTube video about replacing the spindle have a look here may help you and others ,,,,

[michaelconroy]

Thanks everybody.

 

I would have followed your advice to drill out the broken shaft but, my only accident of the day, one of the springs behind the selector switch dropped down the plug hole. I know, I know! I'm kicking myself!

 

M

[BKen1]

Just looking at the loose cable you have .it could be the interior light ...if yours isnt working ...or it connects to a reed switch shown on the wiring diagram but have no idea what tis switch is for trying to download the diagram now.

[michaelconroy]

Thanks BKen1 you could be right - never had an interior light in fridge. But can't see where cable would connect, also connector block is blind on one side.

I see you're near Alicant. We live near Málaga. We rent a villa here just brought van out to travel around in, but was too hot in summer! Taking it back end October.

[BKen1]

michaelconroy - 2017-09-26 6:15 PM

 

Thanks BKen1 you could be right - never had an interior light in fridge. But can't see where cable would connect, also connector block is blind on one side.

I see you're near Alicant. We live near Málaga. We rent a villa here just brought van out to travel around in, but was too hot in summer! Taking it back end October.

 

Hi Micheal it looks to me like it would go in the slot above /next to the fuse(circled ) I would turn the electrics off and see if it fits comfortably (I can be a bit gun hoe sometimes though ) I would give a go.When you say the connector block is blind one side ,the contacts are only on the front of the PC board so they will only be on one side of the plug.

 

Definetly too hot here in Summer for enjoying Spain ....we go off too the pyrennes for summer can still be hot but a least it cools down in the evenings for a good night sleep.June/July and Sept /Oct are the best months for exploring .

[monique.hubrechtsgm]

The dometic fridge i have is a RMDT 8505. Afther 2 years the 230 volt heating element was gone. It heats up the a small pot containing ammonia gas. The same pot for the 12 volt and LPG. You have 5 blue boxes max to set the temp inside. Three blocks are best, freezing your ice blocks within two hours. Five blocks is waste of energy. A track record between Thetford and the above brand can shine a light in the darkness of absorbfridges compared to compressor.But they have to perform in the outdide air . Keep the house as clean as possible and provide max air flow .Your awning above the two screens can raise the temo.