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Dometic RM5310 fridge problem


blackrose

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Came home from work yesterday and found my Dometic RM5310 fridge had stopped working. It's only about 2 years old. 

It was running from the mains at the time, but I can't seem to get it to work from gas. It's not connected to 12v. 

 

Edited by blackrose
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How is the igniter powered (assuming it has an electrical one)? If its a push and click then its Pietzo electric and will not require a power supply but if not the the lack of 12V might explain it (I do not have a manual).

Ah - got one now. Its says the 0 at the end of the number indicates a "battery igniter" so as I can see no sign of an actual battery in the installation manual I suspect it needs a 12V supply.

These fridges need to be all but absolutely level - has your boat developed a list of altered its trim?

Have you checked it actually has a mains supply - check fuses/circuit breakers? Check shoreline bollard breakers.

If it is fairly old the chemicals inside ABSORPTION (not compressor) fridges can separate so you may get lucky, having checked everything else, by turning it upside down and giving the large pipes at the back a good seeing to with the heel of a slipper. Set back the right way up and let it stand for half an hour before setting it to run.

As far as I know this type of fridge still have a mains   and 12V heating elements so if turning it upside3 down does not work the mains element may have failed.

A further thought - you'r not running it from an inverter are you? If so there is every chance the inverter has tripped out on low battery voltage - you have flattened them!

 

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It's being run from the main shore supply and everything else is working on the boat. I just looked at the fuse in the mains plug and it's a 3amp and I don't have a spare. Can you tell if a mains fuse has blown? The trim of the boat has not altered (widebeam).

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6 minutes ago, blackrose said:

It's being run from the main shore supply and everything else is working on the boat. I just looked at the fuse in the mains plug and it's a 3amp and I don't have a spare. Can you tell if a mains fuse has blown? The trim of the boat has not altered (widebeam).

If you have a mulimeter switch it to ohms-resistance and stick a probe on each end of the fuse. If blown you'll get no reading at all.

Edited by bizzard
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On the ohms setting I'm getting a reading of about 0.4 so I assume the fuse is fine?

I just called a service agent in the area and he asked me if the back of the fridge was getting hot on mains. When I said no he said it's likely to be the mains heating element. Is this something I could change myself?

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3 minutes ago, blackrose said:

On the ohms setting I'm getting a reading of about 0.4 so I assume the fuse is fine?

I just called a service agent in the area and he asked me if the back of the fridge was getting hot on mains. When I said no he said it's likely to be the mains heating element. Is this something I could change myself?

Yes...if you can get the fridge out !

Just a resistive heating element , one for 12v and one for 240v .. they are tucked in the side of the insulation around the boiler section of the fridge, and they connect on top of the fridge electrically.

The test to see if they are the problem is again an ohms reading...around 420 iirc for a good mains one...it's probably gone open circuit if it hasn't taken the fuse out.

Replacements available from online caravan spared suppliers ...

Cheers 

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45 minutes ago, bizzard said:

If you have a mulimeter switch it to ohms-resistance and stick a probe on each end of the fuse. If blown you'll get no reading at all.

Actually you will - you will get a    1 on the wrong side of the scale that means infinity. Better use the beep test if the meter has one.

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1 hour ago, mross said:
  • Can you plug something else into the socket, to see if it's working - a fan or a table lamp?

Yes, the socket is fine.

2 hours ago, Tony Brooks said:

Actually you will - you will get a    1 on the wrong side of the scale that means infinity. Better use the beep test if the meter has one.

Is that continuity? I just did that and got a beep. I think the fuse is fine.

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The service engineer told me to unplug the fridge and do a resistance test on the mains element. Do I just set the meter to ohms and then put a probe on each end? He told me resistance was proportional to temperature and at that point it started to go over my head. The back of the fridge is completely cold on the mains so I'm not sure if temperature is relevant? 

Edited by blackrose
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Yes. set to resistance.

Hold the two probes/clips together tightly and make sure the meter reads zero close - if not try changing the battery.

Connect to the DISCONNECTED ends of the element and take reading.

The most likely mode of failure will be an open circuit. If it had short circuited the fuse shoudl have blown.

A 1 on the wrong side of the meter window means an open circuit - burnt out element.

A higher reading, probably something like 200 hundred, means the element is probably OK.

Yes the resistance will rise as the element gets hot but cold it should be a lot more than zero.

Warning - most of boater's resistance testing is done on the 200 ohm range and a working element might have a higher resistance than that giving you the "1" on the 200 ohm range. so if you get the "1" step up through higher resistance ranges. If it stays at 1 the element has had it.

 

 

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24 minutes ago, Tony Brooks said:

Yes. set to resistance.

Hold the two probes/clips together tightly and make sure the meter reads zero close - if not try changing the battery.

Ok, perhaps I need a new battery in my meter because on the ohms setting with the probes pressed together I'm getting a reading of 3.2

I'll change the battery and test the fuse again.

Edit: With the probes held together I'm getting the same reading with a new battery! Do I have the probes connected to the correct ports: Red to V, ohms, continuity port; Black to COM port? I have a Range button on my meter - is that relevant?

Edited by blackrose
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43 minutes ago, blackrose said:

Edit: With the probes held together I'm getting the same reading with a new battery! Do I have the probes connected to the correct ports: Red to V, ohms, continuity port; Black to COM port?

Yes,

You have probes connected to correct place.

If everything is clean and corrosion free (including the battery compartment), the probes tight in the sockets, and the battery is a new oner, recording a reading of 3.2 ohms when 0 ohms is expected indicates the meter is not in good working order.

It may be good enough to make sense of what Tony is suggesting, because you are attempting to measure something a lot bigger than 3.2 ohms and a lot smaller than "infinity" ohms, and absolute accuracy is unimportant, but I'm wondering if the resistance range on your meter can be relied upon at all?

What make and model is it?

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Try twisting the leads in the meter sockets. Its about what I expect from cheaper meters when set to 200 ohms, try K ohms It will probably reaad zero. If not just subract whatever it reads with the probes together on your chosen scale form the result.

Alan is right, it is good enough for what you are ding on the element, but its confusing at first for the fuse.

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15 minutes ago, mross said:

On some meters there is a thumbwhheel on the side for zeroing.....................

This was certainly true on analogue ones, but I've yet to have it on any of the digital ones I have ever owned.

I have always found it easier to do the type of testing talked about here on a meter with a dial, rather than digits, but I no longer have an analogue meter that works reliable on resistance, (funnily enough it is that thumb-wheel that has packed up in the one I can still use for other purposes, but no longer for ohms!)

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55 minutes ago, alan_fincher said:

 

What make and model is it?

Fluke 75 III

45 minutes ago, Tony Brooks said:

Try twisting the leads in the meter sockets. Its about what I expect from cheaper meters when set to 200 ohms, try K ohms It will probably reaad zero.

What's K ohms?

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Just now, blackrose said:

Fluke 75 III

Blimey, any Fluke ought to be able to do far better than read a short circuit as 3.2 ohms!

Are you sure it isn't actually measuring .32 ohms, (or .032 ohms)? :wacko:

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The fridge keeps cutting out on gas. 2 years ago I had the same problem and had it repaired under warranty. I think they replaced a gas regulator on the fridge? Anyway it worked fine after that, but now it's doing the same thing again - cutting out after about an hour. Could it be that it's getting too hot and that's a safety feature as it's about 30C on the boat and probably more at the back of the fridge?

2 minutes ago, alan_fincher said:

Blimey, any Fluke ought to be able to do far better than read a short circuit as 3.2 ohms!

Are you sure it isn't actually measuring .32 ohms, (or .032 ohms)? :wacko:

No definitely 03.2 ohms.

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Unless things have marched on Elextrolux/Dometic LPG fridges are about the most unsophisicated thing imaginable.  The only safety feature I'm aware of when running on gas is the FFD on the burner, as they can easily blow out.

I'm happy to ne proved wrong, but planned cutting out on getting too hot is more sophisticated than I have ever seen, (admittedly always fairly old models).

Your Fluke also sounds unwell, unless, as has been suggested it requires some setting of the zero ohms value - not something I have come across on a digital meter, (but then I can't afford a Fluke!).

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I've turned the gas/temp adjustment on the fridge up to full to see if that makes any difference. Perhaps it's a blocked jet? It seems to cut out when it switches from full flame down to the pilot light. Could it be a faulty thermostat? 

25 minutes ago, alan_fincher said:


Your Fluke also sounds unwell, unless, as has been suggested it requires some setting of the zero ohms value - not something I have come across on a digital meter, (but then I can't afford a Fluke!).

That's what you get for buying second-hand on ebay I guess. It cost me £50 about 10 years ago. 

1 minute ago, blackrose said:

I've turned the gas/temp adjustment on the fridge up to full to see if that makes any difference. 

No, that hasn't worked...

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1 hour ago, blackrose said:

Fluke 75 III

What's K ohms?

A Fluke is not a Maplin special and I would expect it to read zero.

As its a Fluke its probably auto-ranging so you only set it to ohms and then read the display to see what range it has set itself to. If it  has that "1" on the right it will probably be the M ohm scale. K ohms = 1000 ohms so 3 K ohms = 3000 ohms  M ohms is much larger than that and as an electrical as opposed to electronics chap I have had no use for them but probably a million ohms.

 

 

 

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On K ohms my meter is reading 0.01 with the probes connected together.

I can't figure out how to get the mains element out. It only lifts a few inches and then hits the metal flue surround?

IMG_20170709_161956.jpg

Can I test the element in situ? Where do I put the probes?

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