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Dometic 3 way fridge not working on 12v?


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Hi everyone, apologies for the question, but...  We have recently bought a 2004 fiat ducato 2.0L Carioca 656 motorhome.

It came with a few issues which I am working through, however I am lost with the fridge on 12v issue. After reading through the forums, I understand that it will only work on 12v if the engine is running, however, with it running I don't get a light on the fridge. I understand it could be a fuse issue, there are 4 fuse boxes and a C16 MCB on the van, so not sure where exactly to look. The photos show the fuse box behind the drivers seat, the fridge and the MCB under the stove (next to the fridge), there are 2 fuse boxes in front of the passenger and driver, then 1 in the engine bay. I have checked these and found no blown fuses (as far as I can tell). The leisure battery is under the passenger seat (we bought a new one) and I think there is an inverter under the drivers seat. Can anyone help please?

Thanks in advance

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Yes that's the one. The other option is a burnt out heating element, someone on here should be able to tell you how to check that, although I think the light still comes on with that problem.

Edited by colin
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There are two typical ways of wiring the 12 Volt supply to the fridge on that age of MH.

First is the more usual way and this is a drawing from Clive Motts website https://motts.org/SPLIT CHARGING SYSTEM.htm

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On a Ducato the two relays and fuses are usually mounted to the scuttle centrally just below the windscreen. One fuse and relay (R2) controls the charging of the leisure battery and the second fuse and relay (R1) the fridge.

If you only have one fuse and/or relay then your MH may be wired the 'other' way. Here the supply for the fridge relay is taken directly from the leisure battery but is still controlled by the Alternator output D+ signal. The downside of this version is if the split charge relay/fuse fails then the fridge will still working when the engine is running but will flatten the leisure battery in a short time.

Does your leisure battery receive a charge whilst the engine is running? The best way is to measure the voltage at the battery terminals then start the engine and watch for the voltage to rise, ideally to over 14 Volts.

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Based on an online advert for a 2004 CI Carioca 656, the control-panel may be a Nordelettronica NE101C3 unit as shown below

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If that's correct in Antony's case, there is relevant information about the panel in the attachments on a posting here

https://wildcamping.co.uk/threads/carioca-control-panel-light.28189/

and a GOOGLE-search on Nordelettronica ne101c3 might also provide some useful guidance.

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Hi, the control-panel is a Nordelettronica NE101C3. the 'blown fuse' light has never come on. I have took both seats out and what I thought might be an inverter is actually the battery charger (see photo). There doesn't appear to be any inline fuses, other than the ones shown in the black cases on the leisure battery and charger (are these what you mean?). I could not find any fuses in the engine bay near the battery or under the scuttle (unless the photos show them?). I have ordered a multimeter to try and test what I can. Is there any other advice or something that can be seen from the photos?

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OK

Has the fridge actually got a suppy of DC when the engine is running ?

Was the fridge working with the engine running on DC when you purchased the vehicle?

This is step one 

Regards

Edited by onecal
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Being newbies we didn't ask the right questions or check the right things when we bought it (i.e check the fridge on 12v). The guy told us he never used gas and only used EHU sites. We discovered afterwards he had been a bit disingenuous with us, the gas isolation valve on the fridge was seized and all ignition system needed cleaning out, the hot water boiler needed a bit of playing with to work and also there was a damp issue from a bodge repair. I have worked through and sorted most of the issues, but the fridge on 12v is still there. I believe it has not worked from before we bought the motorhome.

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Ok

So , Well done you will get there 

Re the fridge

Start with the simple things first 

Check if you have a 12v DC supply to the fridge itself first, (when the engine is running) is the very first port of call 

Is your panel the exact same as Derek posted  or have they changed it ?

Regards 

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as far as I know the panel works fine, there has been no fuse fault showing on the panel, the gas and 230v electric both now work on the fridge, the heater elements are shown in the photos and they are not in the flue but inbetween the fins. they go over the fridge internally and drop unseen behind the panels, all the wiring in the lower inspection cover are there in the photos. I am awaiting a multimeter delivery to perhaps find the issue, but as of now cannot find any fuses or relays relating to the 12v for the fridge, so am not sure where to go.

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Hi Onecal, thankyou for your help, I am hopefully getting a multimeter tomorrow so I can check if I am getting current to the fridge, just not sure which wires to test etc, so perhaps need some guidance here....

I definitely know that 230v and gas do power up the fridge as we have used them on weekends away, it is just annoying that I can't seem to be getting anywhere with the 12v side.

I really appreciate everyone's input with this issue, and anything I come across whilst in my motorhome will be willingly passed on. 

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Hi

When you do ,check the 12v DC fridge heater element to see is it getting a good DC supply

When the engine is running and DC selected for fridge (Red wire in your photo)

Please make sure your 220/230 V AC supply  is diconnected first 

You then can continue in safety

Services activated by D+ F1: 15A fuse connected directly to the battery auto

F2: 5A fuse connected to the external light switch to power external light.

F3: 10A fuse connected directly to the service battery to power heaters/boilers and ignite gas (cooker, refrigerator, etc.).

F4: 10A fuse connected to the pump switch to power water pumps.

F5: 10A fuse connected directly to the service battery to power electric step.

F6: 20A fuse to power fridges. F7: 15A fuse connected to the master light switch to power light group _1

F8: 15A fuse connected to the master light switch to power light group _2.

The outputs for internal light (lights_1 and lights_2), external light and pump are activated directly by the relevant keys on the control panel. - The internal light switch also operates as a master switch for external light. - The external light goes out automatically when the engine is running. -

If the voltage for the service battery goes below 10V for more than one minute, the NE129 distribution panel automatically turns off all power to the lights and pump. The coupling relay and the three-way fridge relay are enabled directly by the D+ signal (or engine ignition key). The coupling relay recharges the service battery through the alternator with the engine running. The fridge relay powers the three-way fridge at 12V, with the engine running. - Both relays are excited when the ignition battery exceeds 13.4V and automatically de-excite when the engine is turned off or the battery ignition voltage is below 12.5V.

Regards

Edited by onecal
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45 minutes ago, antony driffill said:

Hi Onecal, thankyou for your help, I am hopefully getting a multimeter tomorrow so I can check if I am getting current to the fridge, just not sure which wires to test etc, so perhaps need some guidance here....

I definitely know that 230v and gas do power up the fridge as we have used them on weekends away, it is just annoying that I can't seem to be getting anywhere with the 12v side.

I really appreciate everyone's input with this issue, and anything I come across whilst in my motorhome will be willingly passed on. 

Safety first. On the connector block shown in the photo above the brown and blue wires are the 240V mains element supply and will probably be live at 240V if vehicle is plugged into mains. The green/yellow wire is the mains earth connection.

I am looking at my Dometic RM 7000 series installation instructions dated 10/2005.

The red and white wires at the LHS of the terminal block are the element supply towards the fridge. These wires connect to red and black which enter the flexible conduit.  It is these two wires that should supply nominal 12V to the element when the engine is running.

The violet, and black wires are the control supply to the fridge, which is required whenever the fridge is in use. I note that the negative (black) wire has been connected in  parallel with the element negative. The violet (control supply) links with is either a grey or white wire, which also enters the flexible conduit.

I hope that the above helps.

Alan

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