Technical Dometic fridge not working

[Goznald]

Hey,

We recently bought a 2006 Bessacarr with a Dometic 3 way fridge. Unfortunately we fount it's not working on all means of power, no lights etc.

The MCB is operational as it powers other appliances but it seems there is no power going to the fridge.

I've done some research and some say there is a fuse under the bonnet, others have said it could be a dodgy cable.

Does anyone have any ideas they could suggest as I'm borderline about to throw it out.

Thank you!!

 

[the green vanper]

it's not working on all means of power

Hello,

Does it mean it does not run even on LPG?

No idea if your Ducato is the x244 or the x250 model, being produced in 2006 can be both. The original FIAT VIN shall start with ZFA and then the 3 digits will tell you which model do you own.

Have you got the Bessacar owner's manual? It should explain how the frigde works, where are the potential fuses, etc. Usually, at least on the x250 the converter's socket is on the bottom of the B-pillar. On LHD vans it is on the passenger's side, I think it is the same on RHD (but I'm not sure).

In the download section of the forum you'll find a converters' manual for the x250 Ducato model. It will give you some hints how both electric systems are ment to be connected and how the converters' socket works.

 

[rayc]

It does not need mains power to operate the control panel which should come from the habitation 12v supply. The starting point of your investigation should be to find out if the corresponding LED is on when the power source selector is set to either Gas, 230v or 12v and if not why not.

 

[Goznald]

It does not need mains power to operate the control panel which should come from the habitation 12v supply. The starting point of your investigation should be to find out if the corresponding LED is on when the power source selector is set to either Gas, 230v or 12v and if not why not.

No LED's for gas, 230v or 12v

 

[rayc]

No LED's for gas, 230v or 12v

Then you have a DC problem. Have you a manual, does it show the fridge control supply? Perhaps the members of this FB group may be able to provide information https://www.facebook.com/groups/478836955537595

 

[Communicator]

It does not need mains power to operate the control panel which should come from the habitation 12v supply. The starting point of your investigation should be to find out if the corresponding LED is on when the power source selector is set to either Gas, 230v or 12v and if not why not.

I think that I could be excused from thinking that I was looking at a photo of the fridge in my own PVC, which also dates from 2006.

To expand on the excellent advice given by @rayc , the 3 way fridge needs a permanent 12V supply for its control circuits. Also there should be a relay controlled 12V supply which is only available when the engine is running, a gas (LPG) supply, and a 230V supply when conneced to EHU.

On my similar Dometic RM7361 fridge, the 12V control connection is via a 2 core flex with violet, and black wires, of which the violet is the missing control supply, but this will connect with a different colour in the vehicle wiring.

I suspect that your Bessacar will have a Sargent electrical system. A Sargent wiring diagram in my posession shows the relevant wire as being coloured brown/yellow, However which fuse in the Sargent unit supplies this wire is not shown, but Fuse 6 (5A ignitions) is a possibility.

 

[Goznald]

I think that I could be excused from thinking that I was looking at a photo of the fridge in my own PVC, which also dates from 2006.

To expand on the excellent advice given by @rayc , the 3 way fridge needs a permanent 12V supply for its control circuits. Also there should be a relay controlled 12V supply which is only available when the engine is running, a gas (LPG) supply, and a 230V supply when conneced to EHU.

On my similar Dometic RM7361 fridge, the 12V control connection is via a 2 core flex with violet, and black wires, of which the violet is the missing control supply, but this will connect with a different colour in the vehicle wiring.

I suspect that your Bessacar will have a Sargent electrical system. A Sargent wiring diagram in my posession shows the relevant wire as being coloured brown/yellow, However which fuse in the Sargent unit supplies this wire is not shown, but Fuse 6 (5A ignitions) is a possibility.

Looking at the back wiring shows the black/violet cables, all connected. All connectors pulled apart to check for rust and breakages, all seems fine. I think next step is to check the board on the fridge?

 

[Goznald]

It does not need mains power to operate the control panel which should come from the habitation 12v supply. The starting point of your investigation should be to find out if the corresponding LED is on when the power source selector is set to either Gas, 230v or 12v and if not why not.

Yer no lights on when powered up. All cabling looks fine so wondering if it's fridge PCB

 

[The Panda Nut]

My experience is of fridges in the caravan. The LED did not show when running on 12v but the engine was required for this. As the fridge demands such a high current to operate 12v is was only powered by the charging circuit connection. If the gas is not working its a separtae issue. Check the fridge gas isolator tap is still on. Take the jet out and check its not blocked with soot.. Check there is gas at the fridge, clean the ignitor and thermocouple while you are there. 240v was when the lights came on. I would say its worth asking for a service before throwing it out. The last fridge I had lost its refrigerant gas and just would not work. They can be regassed but it was very costly and there were few people who could do this when I looked into it some years back. I never did it. We used 12v when driving and went without which is not practical. It sounds suspiciouly like our refrigerant loss. I hope you manage to get it back upand running.

 

[Communicator]

Looking at the back wiring shows the black/violet cables, all connected. All connectors pulled apart to check for rust and breakages, all seems fine. I think next step is to check the board on the fridge?

Before pulling the fridge apart, have you confirmed +12V present on the violet wire?

 

[Goznald]

Before pulling the fridge apart, have you confirmed +12V present on the violet wire?

If I'm honest I am new to this so not sure best way to check. I know I would need a multimeter but is it that simple?

 

[Communicator]

If I'm honest I am new to this so not sure best way to check. I know I would need a multimeter but is it that simple?

A multimeter will be useful, but they are very sensitive, and may not reveal a high resistance connection. Perhaps you could make a 12V test lamp from an older style sidelamp bulb with metal cap, and a length of insulated wire. Twist bared end of wire tightly around the metal part of bulb, and cover with a small amount of sticky tape. With the centre contact of the bulb held against a known earth (fridge body should be earthed), use free end of wire as probe. Do be prepared for the bulb to get hot. Take care.

 

[Goznald]

A multimeter will be useful, but they are very sensitive, and may not reveal a high resistance connection. Perhaps you could make a 12V test lamp from an older style sidelamp bulb with metal cap, and a length of insulated wire. Twist bared end of wire tightly around the metal part of bulb, and cover with a small amount of sticky tape. With the centre contact of the bulb held against a known earth (fridge body should be earthed), use free end of wire as probe. Do be prepared for the bulb to get hot. Take care.

The free end, is it as simple as placing in one of the blocks that feeds the fridge?

Like that block or the feed directly into the board?

 

[Communicator]

The free end, is it as simple as placing in one of the blocks that feeds the fridge?

Like that block or the feed directly into the board?

Yes, but you could separate the connector and probe the supply side of whatever connects with the violet wire going to the fridge.

 

[Goznald]

Yes, but you could separate the connector and probe the supply side of whatever connects with the violet wire going to the fridge.

Something like this?

 

[Goznald]

Something like this?

Is it that simple because if so the light doesn't switch on from any cable entry

 

[rayc]

Is it that simple because if so the light doesn't switch on from any cable entry

I really think you would benefit from a caravan / motorhome engineer spending an hour or so investigating your problem.

 

[Communicator]

Is it that simple because if so the light doesn't switch on from any cable entry

General idea, but that is a mains voltage bulb. You need as specified, a vehicle sidelamp bulb 12V 5W rating. Do not use this assembly on 230V mains supplies.

 

[rayc]

The bulb will have a positive and negative so you need to connect with a twin cable. If I interpret your photo correctly you have used a twin cable with both wires twisted together and only connected to the bulb mains neutral. Take care.

 

[HughJampton]

There will be two 12v fuses associated with the fridge.

At that vintage the one that protects the 12v "cooling" circuit is likely (on a Swift Group model) to be under the large black plastic cover to the rear centre of the engine bay, along with fuses protecting each of the two batteries. You should also find the split charge and fridge relays there. Useful to know, but if you have no power at the controls, it isn't the prime thing to check.

The control circuit should be separately fused, but the location would depend on the model and year. If you're lucky it may be with the main bank of fuses (on the PSU) but it looks more likely to be a single fuse, and in that case I'd be looking near to the leisure battery, then the vehicle battery (apparently both have been used as the source at different times), and then through the fridge vents at the rear of the unit.

It's worth persevering as replacement PCBs are expensive or made of unobtanium, and the cost of a new fridge doesn't bear thinking about.

(Others experiencing similar issues have eliminated some suspected causes by running a temporary 12v feed from the battery direct to the 12v control connection)