# Fridge Wiring for 12v on the move



## colpot (Jun 9, 2008)

I have taken the Fridge out ready for the new one to be fitted. I have a temp Coolbox (mains/12v/gas) in place until I can get the new fridge fitted when we come back from hols in August.

I have the mains in place and working but have 2 feeds for 12v - one is live when the engine is not running, but goes off when the engine is started. The other is a thicker pair of cables which I guess from the wiring diagram goes to the leisure battery (or does it?)
Whether I start the Engine or not there is not voltage on these cables.

I assume the switching is done on the Fridge PCB normally so that when the 12v on the small cable goes off it allows the thicker cable to supply the feed but I am only guessing.

Anyone have any ideas what should be happening on the 12v Supply.
(As temp measure am going to run the 12v mode from the socket in the cab which is rated 190w and the Coolbox is 90w but need to know info for when new Fridge is fitted in August)


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## philoaks (Sep 2, 2008)

When the fridge is running on 12v it will probably be pulling in excess of 10 amps which is why they only work when the engine is running. The feed that you have may come from either the leisure battery or the vehicle battery, dependent on the manufacturer but whichever one it comes from it will be fed via a relay. Normally this relay will be in the open position (no 12v to the fridge) but once the engine is running, the "sense" lead from the alternator will operate the relay and connect the 12v through to the fridge. There will also be a suitable fuse somewhere in the circuit.

If you aren't getting 12v when the engine is running then you may have a fuse/relay issue.

Edit. This relay will normally be external to the fridge. Often they are located under the bonnet but not always !


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## pippin (Nov 15, 2007)

Be careful about running 190W (=15A) from a cigar lighter type socket, even if it it fused at 15A.

It will not like a constant current close to its max rating - they are designed for intermittent use.

There could be danger of fire due to the plug/socket and/or wiring overheating.


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## colpot (Jun 9, 2008)

pippin said:


> Be careful about running 190W (=15A) from a cigar lighter type socket, even if it it fused at 15A.
> 
> It will not like a constant current close to its max rating - they are designed for intermittent use.
> 
> There could be danger of fire due to the plug/socket and/or wiring overheating.


The Temporary Cooler is only rated at 90w so hopefully it wont be overheating?


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## pippin (Nov 15, 2007)

Ah, sorry, I hadn't realised that.

Even so, I would check the temperature of the plug end after it has been on a while.

If it is more than warm to the touch on the palm of your hand then be wary.


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## Pudsey_Bear (Sep 25, 2008)

You should have a proper wiring diagram for the appliance, failing that Google for one, failing that, the fridge does not normally have it's 12v DC cooling circuit supply come from the LBs, it should come via a heavier cable from the split charge relay, and a larger capacity HD relay triggered by the split charge relay, which again is triggered by a cable direct to the alternator or sometimes it picks it up direct from the VB, it gets a little difficult about there as I'm not familiar with your van, if you have another lighter set of 12v DC wires they are most likely for the interior fridge light and the ignitor.

The reason one set of cables goes of is because the builder in their infinite wisdom decided that there would be no need to have any power going tot he fridge light or the ignitor as you would most likely be driving, and the fridge should be switched manually or via a AES to 12v DC via the thicker cables.

When the new fridge arrives it should have all the details you need to sort it out, if not we're only a post away.

Hope you manage to figure it out despite my help


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## VanFlair (Nov 21, 2009)

Hi Kev

Our fridge Dometic 7 series AES runs from the LB's the D+ Wire to signal alternator output goes direct to the fridge so I guess all switching is in the fridge.

I have a solar regulator AES signal going to the fridge D+ terminal and this runs it on solar from the LB's.

Martin


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## Pudsey_Bear (Sep 25, 2008)

It probably Does Martin, but there will be a split charge relay of some type in there somewhere though, as the loads will be too high for direct switching I would think.

A relay is only a big switch to handle greater loads really, triggered by a smaller switch placed more conveniently, or to save it from melting etc.


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## colpot (Jun 9, 2008)

Thanks for the info - I am going to try to use the 12v feed for the Fridge to run the temporary Coolbox while we are on the move but at the moment I cant get 12v to the larger cables when the engine is running. The wiring diagram I have is ok but if only it had the location of relays etc it would save me a lot of hunting. I am thinking either the in line fuse (I havent been able to locate this yet) or the relay need changing.


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## Pudsey_Bear (Sep 25, 2008)

Hmm, sound like you might need an auto sparky, or a useful neighbour who likes a challenge.


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## colpot (Jun 9, 2008)

Well it looks like I have sorted it (with the help of the AA (roadside not alcohol!)
Went to start the van as I wanted to test the 12v feed and it wouldnt start - just turned over.
Thought I must have blown a fuse so tested all the obvious (to me!) ones like fuel pump and starter.
In the end I called Saga (AA) Motorhome Assistance and the very nice Guy turned up within half an hour and set about checking everything I had and then he attached the diagnostics but it wouldnt talk to the Motorhome, so he set about checking some more fuses and he found the Engine Management fuse was blown (he said it has been replaced before).
Now the Van started first turn and I now have 12v feed to the coolbox from the original fridge feed so I dont need to connect to the cab socket, Its a bit of a roller coaster this new to us perfect layout motorhome.
Thanks again for the advice and comments.


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