12V system on auto sleeper

[PatrickS]

Morning. Been a member since last year but this is the first post. Really enjoyed reading posts on here and have found them really useful so thank you.
We bought a 1998 Peugeot boxer autosleeper last year and was told the 3-way fridge didn’t work on 12v so was replaced by a 240 one. We have now refitted a fully working 3-way fridge but it does not work on 12v when engine is running. It works when engine is not running. Have been advised it could be wired wrongly. It should be connected to main battery so it could be on when engine is running. Was told it should not be connected to both main battery and leisure battery so could not be on 12v when parked up.we have to use 240 or gas when parked.
We’re a bit confused as previously we’ve had campervan where the 3-way fridge works on 12v whether travelling or parked up. So any advice would be greatly appreciated.
Many thanks in advance.

 

[trevskoda]

If you have solar and a small inverter then the 230v small fridge is miles better than the old stoneage 3 way units.
Saying that there should be a relay which connects the 12v side to the engine battery when driving, seems something wired up wrong.

 

[colinm]

A three way fridge would normally be connected such that the 12v element only works with engine running.

 

[PatrickS]

It’s not just the fridge that’s not working on 12v when driving. The whole 12v is not working as we tried to plug in a cool box and it didn’t work but yet worked plug into cigarette lighter.

 

[colinm]

It’s not just the fridge that’s not working on 12v when driving. The whole 12v is not working as we tried to plug in a cool box and it didn’t work but yet worked plug into cigarette lighter.

This is common on brittish vans which are built to NCC regs. It won't work when driving if connected to leisure battery.

 

[colinm]

When you say "We have now refitted a fully working 3-way fridge", did you fit it yourself, or did a competent motorhome workshop fit it?

 

[r4dent]

It’s not just the fridge that’s not working on 12v when driving. The whole 12v is not working as we tried to plug in a cool box and it didn’t work but yet worked plug into cigarette lighter

Which cigarette lighter socket did you plug the cool box into that didn't work.

On most vans the 12v cigarette lighter(s) on the dash board are wired to the vehicle (starter). On some MoHos these are only powered when the ignition is on, on some vans they are always powered.

On Most vans the 12v cigarette lighter(s) in the habitation area are powered by the leisure battery. On many vans all 12v supply (well all excluding the control panel and the light in the 3 way fridge) is automatically switched off when the engine is running and is not switched on automatically when the engine is switched off.

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We’re a bit confused as previously we’ve had campervan where the 3-way fridge works on 12v whether travelling or parked up.

A three way fridge that works on 12v when parked surprises me a lot, for two reasons
a) The fridge draws a lot of amps on 12v (when the engine is running it the power is supplied by the alternator not a battery) and will flatten most batteries in under an hour.
b) 12v mode on a 3 way fridge does not cool the fridge down it is only enough to maintain temperature. So using it when parked and opening the fridge to get at the contents would cause the fridge to get warmer.

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A few years ago I wrote a basic guide to electricity in motor home after someone asked why is microwave didn't work in a lay-by.
With respect may I suggest that you may benefit from reading it. https://wildcamping.co.uk/threads/electricity-in-your-motor-home-for-dummies.74748/#post-1000246

 

[PatrickS]

When you say "We have now refitted a fully working 3-way fridge", did you fit it yourself, or did a competent motorhome workshop fit it?

It was fitted by a fully qualified competent workshop and signed off

 

[PatrickS]

Which cigarette lighter socket did you plug the cool box into that didn't work.

On most vans the 12v cigarette lighter(s) on the dash board are wired to the vehicle (starter). On some MoHos these are only powered when the ignition is on, on some vans they are always powered.

On Most vans the 12v cigarette lighter(s) in the habitation area are powered by the leisure battery. On many vans all 12v supply (well all excluding the control panel and the light in the 3 way fridge) is automatically switched off when the engine is running and is not switched on automatically when the engine is switched off.

-----------------


A three way fridge that works on 12v when parked surprises me a lot, for two reasons
a) The fridge draws a lot of amps on 12v (when the engine is running it the power is supplied by the alternator not a battery) and will flatten most batteries in under an hour.
b) 12v mode on a 3 way fridge does not cool the fridge down it is only enough to maintain temperature. So using it when parked and opening the fridge to get at the contents would cause the fridge to get warmer.

---------------------------

A few years ago I wrote a basic guide to electricity in motor home after someone asked why is microwave didn't work in a lay-by.
With respect may I suggest that you may benefit from reading it. https://wildcamping.co.uk/threads/electricity-in-your-motor-home-for-dummies.74748/#post-1000246

Thank you.
The cigarette lighter it worked on is on the dash area. The habitation area ones don’t work with engine on.
I thought the idea of the fridge connected up to the 12v when driving was to keep the fridge cool after it’s been cooled by 240 before it’s disconnected and setting off on journey.

 

[colinm]

Thank you.
The cigarette lighter it worked on is on the dash area. The habitation area ones don’t work with engine on.
I thought the idea of the fridge connected up to the 12v when driving was to keep the fridge cool after it’s been cooled by 240 before it’s disconnected and setting off on journey.

A 3way has 240v, 12v, and gas. The 12v is only for use when driving, the other two are for when stopped. If you look online you should find the installation guide for your fridge, it should clearly explain that the 12v supply to cooling element is only triggered when the engine is running. As I've post earlier, on most (all?) British vans built to NCC regs the 12v leisure battery is disconnected when the engine is running. For a motorhome workshop to not know this is pretty much unforgivable.

 

[r4dent]

The habitation area ones [cigarette lighter sockets] don’t work with engine on.

That is as it should be.
Most of the 12v devices in the habitation (including the 12v cigarette lighters in the habitation are) are powered from the habitation battery and are automatically disconnected when the engine is on.
When the engine is running the fridge should work on 12v because it is powered by alternator.
Some fridge functions (e.g. temperature detection and AES logic) are not wired via the 12v control panel and work at all times unless the fridge is switched off. [the draw from these functions is often the cause of flat leisure batteries for people who have "Switched off 12v at the control panel"]

I thought the idea of the fridge connected up to the 12v when driving was to keep the fridge cool after it’s been cooled by 240 before it’s disconnected and setting off on journey.

That is exactly what 12v fridge is for, it maintains temperature using 12v from the alternator ... it does not cool the fridge.
Which is one of the reasons that I was surprised by your previous campervan which used 12v to power the fridge when parked.

 

[PatrickS]

A 3way has 240v, 12v, and gas. The 12v is only for use when driving, the other two are for when stopped. If you look online you should find the installation guide for your fridge, it should clearly explain that the 12v supply to cooling element is only triggered when the engine is running. As I've post

 

[PatrickS]

Thank you all so much for your replies and education. It’s all very informative and appreciated. Cheers

 

[mariesnowgoose]

Well, I'm none the wiser after that little lot!

For what it's worth: our old Autosleeper (2003 VW Gatcombe) the 12v for the 3-way fridge is definitely only for use when driving.

When parked up it is either gas or 240v hookup, never 12 volt.

As its happens we have never bothered with the 12v when driving, we just leave the gas on

I am totally lost when it comes to the info on "cigarette lighters" in the "habitation area"??
Never owned a van that had a "cigarette lighter" anywhere other than in the driving cab, but that may be just our limited experience and number of vans owned (not many!)?

 

[colinm]

"cigarette lighter" is a common misnomer for a type of 12v socket often fitted in vans.

 

[molly 2]

If the dash power supply.y is not working it is probably the fuse it is in a fuse box passenger side under the bonnet ,
No domestic power is available when engine is running
A 12v fridge would flatten a BATTERY in a few hours
A new compressor fridge is designed to run on 12 v and is the choice for many that replace an old 3 way fridge, and have the battery and solar capacity to run one .

 

[PatrickS]

Well, I'm none the wiser after that little lot!

For what it's worth: our old Autosleeper (2003 VW Gatcombe) the 12v for the 3-way fridge is definitely only for use when driving.

When parked up it is either gas or 240v hookup, never 12 volt.

As its happens we have never bothered with the 12v when driving, we just leave the gas on

I am totally lost when it comes to the info on "cigarette lighters" in the "habitation area"??
Never owned a van that had a "cigarette lighter" anywhere other than in the driving cab, but that may be just our limited experience and number of vans owned (not many!)?

Wow how safe is it to travel with the gas on?

 

[r4dent]

Wow how safe is it to travel with the gas on?

There are two schools of thought about that.

No doubt both will be posted in great detail.

 

[molly 2]

Some older fridges would run on gass when traveling but they should be switched off or to 12 v when traveling , big fire risk after an accident if gass fridge is running

 

[wildebus]

Morning. Been a member since last year but this is the first post. Really enjoyed reading posts on here and have found them really useful so thank you.
We bought a 1998 Peugeot boxer autosleeper last year and was told the 3-way fridge didn’t work on 12v so was replaced by a 240 one. We have now refitted a fully working 3-way fridge but it does not work on 12v when engine is running. It works when engine is not running. Have been advised it could be wired wrongly. It should be connected to main battery so it could be on when engine is running. Was told it should not be connected to both main battery and leisure battery so could not be on 12v when parked up.we have to use 240 or gas when parked.
We’re a bit confused as previously we’ve had campervan where the 3-way fridge works on 12v whether travelling or parked up. So any advice would be greatly appreciated.
Many thanks in advance.

lots of previous replies and some good info given

Now as far as the line goes

We have now refitted a fully working 3-way fridge but it does not work on 12v when engine is running. It works when engine is not running. Have been advised it could be wired wrongly

Something is not right as it is working in the opposite way it should as you are now aware. Ignoring the competence or otherwise of anyone who has worked on your motorhome, it kind of sounds as if a relay has been replaced and the connection made to the wrong terminal?

On your 1998 Motorhome, you almost certainly have an early Sargent wiring system, and the relay for the Fridge power from the Starter Battery will be under the bonnet - see the diagram below where I have put a Red box over the relevant bits

Wiring Diagram Swift Suntor_Sundance 2002 by David, on Flickr
This is described as a Swift Sundance wiring diagram but the same diagram is applicable to many British Motorhomes of this era, including I am sure the Autosleepers.

What MIGHT have happened is when the problem was being investigated, the normal relay - a standard 12V 4-pin relay - may have been replaced with a 5-pin relay? A perfectly acceptable thing to do, but it gives the chance to misconnect the output to the fridge and results in the fridge only getting 12V when the engine is off, and stopping getting the 12V when then engine is running. Precisely what you are describing and I can picture someone making that mistake quite easily - but I can't so easily picture them not realising there was a problem and then correcting it quite quickly.

For the technical bit how it works:

• A 4 Pin Relay has an single pin out - Pin 87 - which is "NO" (Normally Open) and this is as it says 'Normally Open' until the relay is activated, for example by the engine running. If the engine is off, Pin 87 is open and no power. If the relay goes faulty, it can be stuck open or it can be stuck closed. Neither of those sound like they apply to your problem.
• A 5 Pin Relay is like a 4 pin one but as well as having a Pin 87 "NO", it also has a Pin 87a "NC" (Normally Closed) connection.
  You will have power into the relay on Pin 30, which is the supply. Pin 87 is the normal output and same as the 4 Pin relay, it is connected to the supply on Pin 30 when the engine is running and is open when the engine is off. However the Pin 87a is the reverse - it is connected to the Pin 30 supply when the engine is OFF, and then is disconnected from the supply when the engine is ON.

The reason for the problem may or may not be as I describe it above, but it is the only logical reason that comes to mind without someone doing some very strange rewiring. Checking the relay is a good first step and you can pull out the relay from its holder and see if it has 4 or 5 pins to start with. (note you have 2 relays side by side and it will not be obvious which is which, so look at them both).
If 4 pins, something else. If 5 pins, check further.
If you click on this link - https://www.easycarelectrics.com/normally-open-and-normally-closed-relay-diagram-symbol/ - and scroll down you can see the pin layout of both the 4-pin and 5-pin relays