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Dometic 3 way fridge not working on 12v?


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You need to do the test that Onecal has suggested at the JP11 D+ connection , without D+ the fridge and split (leisure and starter batteries) charging will not work and that connection needs to be checked first.

Edited by Labby
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Hi, not sure what you want me to test, When I tested JP11 connector before, I was getting a 12v reading on 1 and 2 red cables, when I tested 3 red cable there was nothing with or without the engine running and with or without the fridge set to 12v. The wires from the NE129 fusebox go straight into the black corrugated trunking that goes around the van, threre are no visible inline fuses or relays in any of the areas mentioned by people, or anywhere else I have looked... The leisure battery has no other cables running from it, other than the positive and negative. 

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There should be a signal to the 3rd cable that comes from the Fiat alternator charging system and that needs to be traced back to find either a poor/broken connection or faulty/blown fuse , I do not  have any information regarding the wiring or where the cables may be joined on your type of Motorhome but maybe someone else can help if they know your model  ,  ( I will look for this information but do not know if it is avaliable )  When on EHU what voltage do you get at your leisure battery  as it is very low and your charger may not be switched on/working or need its connections checking.

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when it is on EHU i'm pretty sure it charges the leisure battery (will test for sure tomorrow).

I am not convinced there is the front end cabling for the 12v fridge. With no visible inline fuses/relays in the engine bay or anywhere else, perhaps it was never finished properly when being built, or one of the previous owners changed the alternator or battery and didn't refit the wiring loom or whatever...

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It is not really a problem if  the 12v fridge cooling when under way does not work as long as the gas operation and 230v side work ok , BUT , the starter and leisure batteries should both be being charged from the engine alternator , via the NE129 ,  when under way , as this is needed to keep the leisure battery charged  for the operation of the habitation 12v electrics , water pump , heating controls, lights etc when  on non- EHU sites or parked up.(unless you only stay on sites with EHU and the 230v charger is working)

It would be worth finding a Motorhome/Camper/Caravan electrician and sorting out the D+ signal , or wiring another supply into your NE129 PSU , if only to have  the split battery charging working as it should.

Edited by Labby
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Hi Antony

Looks like you have found one fault .  You did say you had damp issues ? We have no way of knowing what changes may have been made to the wiring of your unit  

I have sent you diagrams and photos where fuses etc' are.  Again I have no idea  what may have been added or deleted from your wiring circuits.  What I have sent you in both photos and diagrams with test points included  should make it very easy to diagnose any issue

I think at this stage i have to agree with Labby and you should engage a good auto electrician as you have done some of the groundwork. 

 This circuit Is not a difficult fix but you may also need to have the N129 board checked or repaired aswell and this may not be within  your area of expertise. 

Kind regards

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Hi guys,

thankyou for all your help and guidance! I agree with you that I need to get an auto electrician to have a look, as I am no expert in this area. It is frustrating for me not to be able to resolve the issue, however, there are other things I can be doing to improve our MH. We are currently looking at fitting solar power and/or a power station, so no doubt I'll be on the forums again soon bugging everyone!

Thanks again

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20 hours ago, antony driffill said:

Hi, not sure what you want me to test, When I tested JP11 connector before, I was getting a 12v reading on 1 and 2 red cables, when I tested 3 red cable there was nothing with or without the engine running and with or without the fridge set to 12v. The wires from the NE129 fusebox go straight into the black corrugated trunking that goes around the van, threre are no visible inline fuses or relays in any of the areas mentioned by people, or anywhere else I have looked... The leisure battery has no other cables running from it, other than the positive and negative. 

I have provided you with the test points with photos and diagrams  that should have made the diagnostics a little easier

A lot go on fourms looking for a quick fix , sadly the quick fix, is not the fix for all , When you do your groundwork  you may pick up quite a lot that may serve you well in the future 

I have asked you a few times as to your water leak ? (dampness) Well here is one common quick fix (again may not solve yours) Check your fuses again  Start with the 20A. Pull it in and out a few times and then replace it with a new one  Do that with the others also

.40AfusefromB2battery.png.589827953a420f8fd4a9c919303d8c93.png

Check your B2 Habitation battery it should have a 40A fuse on that line marked on attached diagram  to JP10 connection block This is why i asked was there a loose wire along the side of the battery (sometimes they do not get reconnected on replacing the battery (quick fix reconnect ,if it's there) on the batteries

Your engine battery B1 should have a similer arrangment as per diagram attached  except the wiring goes to JP11 connection block

Note:- 1A fuse on D+ line to connector block JP11 on your N129 board

You need to establish Voltage on this line as per my previous post 

Hope this helps a little and does not cause you more confusion

Regards

Engine battery B1 40A fuse.png

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4 hours ago, antony driffill said:

Hi guys,

thankyou for all your help and guidance! I agree with you that I need to get an auto electrician to have a look, as I am no expert in this area. It is frustrating for me not to be able to resolve the issue, however, there are other things I can be doing to improve our MH. We are currently looking at fitting solar power and/or a power station, so no doubt I'll be on the forums again soon bugging everyone!

Thanks again

There would be no point fitting solar until you get the split and mains charging sorted out , solar is useful for helping to keep the batteries fully charged when in storage etc but you would not be able to rely on just solar to power the 12v habitation side of things.

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Hi guys,

Sorry for not clarifying the damp issue. We had a bad leak at the rear coming from a badly repaired 'sprung' trim on the roof edge above the 'boot' door and also a leak on the seal on the same door, basically I had to dismantle the door and frame then rip off the plywood and polystyrene and replace it all after taking off all the edging trim and resealing/screwing it down again. I got the new bits from O'learys in Hull, he was most helpful. So far I think its sorted, however, we are keeping an eye on it every time it rains.

I have double checked on the leisure battery and it is charging ok on EHU. 

The 40amp inline fuses, would they be what I mentioned before about the metal strips in the black plastic cases inline with the charger and leisure battery?

20240907_090034.jpg

20240907_091323.jpg

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10 hours ago, Labby said:

There would be no point fitting solar until you get the split and mains charging sorted out , solar is useful for helping to keep the batteries fully charged when in storage etc but you would not be able to rely on just solar to power the 12v habitation side of things.

I think the thousands of people like us who use solar to charge hab batteries for weeks at a time would disagree with you.

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I agree  people (including myself) use solar to keep a working charging system topped up , the normal charging system is not working in this case so the power supply would be working on solar only leading to flat batteries , if it was fitted before the system was repaired,

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On 12/09/2024 at 07:01, antony driffill said:

Hi guys,

thankyou for all your help and guidance! I agree with you that I need to get an auto electrician to have a look, as I am no expert in this area. It is frustrating for me not to be able to resolve the issue, however, there are other things I can be doing to improve our MH. We are currently looking at fitting solar power and/or a power station, so no doubt I'll be on the forums again soon bugging everyone!

Thanks again

Let us know how you get on 

Regards

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