12v to fridge while engine is running

[Tantalus]

I have an unsolved issue. I recently bought a new 12 volt only compressor fridge, it's great in that it is smaller than the 3-way but has much more food capacity. Unfortunately it stopped working in southern Spain but has started again now we are home!

I also discovered that the wiring in our van cuts off the fridge when the engine is running. We have always known that the loo doesn't flush, and the cooker igniter doesn't work, with the engine running but never realised the fridge until we had this new one, there's a light in it. Is there any reason for this set up or are we ok to get it all changed?

Also wondering if the wiring to the new fridge needs to be heavier, it was connected in the same way as the old one except that the mains cable, which is separate, is now disconnected. We have plenty of solar and a big domestic battery. The readout for the battery has been 85% at it's lowest and 12-13 volts almost always.

 

[Jimbohorlicks]

The 12 v system usually cuts out when the engine starts.you will probably need to wire the 12 v fridge differently.

 

[jezport]

Compressor fridges are usually wired differently to way3.

 

[Lenny HB]

If it's a Brit van there will be a relay that turns off the hab electrics when the engine is running also the wiring will be well undersized.

 

[NigelNovice]

The 12v on my 3 way only works when the engine is running, to big a drain on battery, run on gas or EHU with engine off

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[Spriddler]

The 12v on my 3 way only works when the engine is running, to big a drain on battery, run on gas or EHU with engine off

That's perfectly normal for m/h's with an absorption fridge but the OP has said that his is a compressor type.

 

[Itsmcb]

If your new fridge was connected to the old 3way fridge wiring it will only work when the engine is running as the supply is from the alternator via the starter battery and a relay.
Your habition 12v cuts off when the engine is running via another relay as mentioned previously.
You need to run a separate supply from whichever battery you want to run the fridge from (usually the habitation battery).

 

[Sheddy]

We had to have a separate 15a fused supply direct from the leisure batteries for our recently fitted compressor fridge freezer. I am currently tidying up the wiring fitted by the Thetford agency, it was not dangerous but a complete mess.

 

[NigelNovice]

That's perfectly normal for m/h's with an absorption fridge but the OP has said that his is a compressor type.

yes, I meant it to come over as itsmcb has said, the12v leisure battery power shut down when engine runs

 

[Billylou]

If it's a Brit van there will be a relay that turns off the hab electrics when the engine is running also the wiring will be well undersized.

Hi Lenny. I was thinking of putting a small compressor fridge/freezer under the bed and run it off 12v. Is it safe to assume that the fridge will be powered whilst the engine is running as the van is German built? Many thanks

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[Lenny HB]

Hi Lenny. I was thinking of putting a small compressor fridge/freezer under the bed and run it off 12v. Is it safe to assume that the fridge will be powered whilst the engine is running as the van is German built? Many thanks

Do you mean while the engine is Not running?

 

[funflair]

Do you mean while the engine is Not running?

No I think he means when it is running unlike the fridge supply in the question by the OP, Billylou if you wire it to the habitation 12v it should have power all the time but simple to check before you go to any trouble.

 

[Reallyretired]

If its like my German motorhome it will be powered with engine running and not running.
The relay cutting off all power to the hab electrics seems to be a British inconvenience.

 

[Tantalus]

It's a Merc, and I am a She!
I want the fridge to run from the house battery while the engine is running so I shall need an electrician to sort it out. I think larger wire will be a good idea too. Thanks all.
Apols, I should change my camper pic

 

[Billylou]

Many thanks everyone. I wanted to know if I plug a portable fridge freezer into my Hella socket (via adapter to UK 12v) it would run whilst driving as well as when parked up. Having read some of the above I wanted some clarity. Thanks a million

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[Itsmcb]

Many thanks everyone. I wanted to know if I plug a portable fridge freezer into my Hella socket (via adapter to UK 12v) it would run whilst driving as well as when parked up. Having read some of the above I wanted some clarity. Thanks a million

Best way to know for sure is to plug something in (or use a test meter) and try it with the engine off and running. It's just a guess otherwise as it depends how (and where from) your socket is powered

 

[Billylou]

Best way to know for sure is to plug something in (or use a test meter) and try it with the engine off and running. It's just a guess otherwise as it depends how (and where from) your socket is powered

Think you’re spot on. Going to buy the a Hella adapter and give it a go. Many thanks

 

[RogerIvy]

We replaced our old 3-way with a 12v compressor fridge. We didn't use the existing 12v supply, taped it off and ran new wires direct from a bus bar we installed near the battery. Works really well!

 

[tonka]

Many thanks everyone. I wanted to know if I plug a portable fridge freezer into my Hella socket (via adapter to UK 12v) it would run whilst driving as well as when parked up. Having read some of the above I wanted some clarity. Thanks a million

The power should be available both when running and stationary but may still need the power switched on at the control panel first.
Personally I would remove the 12v cigarette plug and fit a proper Hella one, better connection and avoids joints that could come apart, move or make a poor connection.
Most 12v sockets are rated 120-150w so your best to check the power requirements of the fridge first.

As mentioned above, the power not operating inside the habitation area while running is a bit of a British specification, all my previous vans were Autotrails and never had power in the back.

 

[Badknee]

I really get cheesed off with this uk way of shutting the leccy off in the hab area when on the move, Why? Our Hobby didn’t do this and neither do the hundreds of thousands of other mainland Europe built vans as far as I can tell.

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[Lenny HB]

I really get cheesed off with this uk way of shutting the leccy off in the hab area when on the move, Why? Our Hobby didn’t do this and neither do the hundreds of thousands of other mainland Europe built vans as far as I can tell.

Must be a PIA for anyone with a Brit van, two reasons they do it, can't stop building them like caravans & saves them a fortune in EMC testing all the components.

 

[Badknee]

Must be a PIA for anyone with a Brit van, two reasons they do it, can't stop building them like caravans & saves them a fortune in EMC testing all the components.

I can understand it to some extent on caravans ‘cos you don’t know what the hells going on back there. Total mayhem and you don’t know but that’s completely different to mohos.

 

[autorouter]

Can I suggest that the OP adds a small fusebox, maybe 6-way, wired directly to the leisure battery (via a nice big fuse of course). From there it's very easy to wire a fridge, extra 12V sockets etc. You could get a fusebox with a built-in negative busbar, which will make the wiring even easier in a typical motorhome. Something like this:

Standard Blade Fuse Box With Positive & Negative Busbars - 6 Way

6 way standard blade fuse box with 2 positive busbars & 1 negative busbar. The -ve busbar is useful to common cables back to the battery -ve terminal.

www.12voltplanet.co.uk

 

[Littlewheels]

It's a Merc, and I am a She!

Love it…..You tell ‘em girl.

 

[pappajohn]

A 3 way fridge should get power from the alternator/battery with the engine running....that the idea of a 3 way.
Turn off the engine and it reverts to 230v, if no mains it reverts to gas.
Saying that, the modern unnecessarily over complicated control units may now cut power.

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[pappajohn]

I can understand it to some extent on caravans ‘cos you don’t know what the hells going on back there. Total mayhem and you don’t know but that’s completely different to mohos.

It's a national caravan council (NCC) requirement and is for NCC approve converters....ie:- British

 

[Littlewheels]

Must be a PIA for anyone with a Brit van, two reasons they do it, can't stop building them like caravans & saves them a fortune in EMC testing all the components.

Typical British short cut, never minds whats best, put in what we can get away with.

 

[autorouter]

A 3 way fridge should get power from the alternator/battery with the engine running....that the idea of a 3 way.
Turn off the engine and it reverts to 230v, if no mains it reverts to gas.
Saying that, the modern unnecessarily over complicated control units may now cut power.

That is 100% true, but the OP says

I recently bought a new 12 volt only compressor fridge, it's great in that it is smaller than the 3-way but has much more food capacity

so it's a compressor fridge that needs to be wired so that it's connected to the leisure battery all the time. Or if you want to get complicated, wire it so it works from the alternator/starter battery while the engine is running, and switches to the leisure battery when it stops.

 

[Billylou]

So when I plug in a 12v device, via a Hella adapter, and test it with the engine running it’s all good. On the strength of that I purchased a Mobicool fridge freezer. The good news is the 12v plug has a sleave on it which once removed can be plugged straight into the Hella socket meaning I no longer need the adapter.