# 12v habitation isolation when engine running



## Beemer (Dec 14, 2010)

Yet again I call upon the more experienced on this forum to help me with a small problem with my 'van.
My 12v habitation electrics (except fridge) isolates when the engine is running, I wish to allow my son who travels in the rear of the van to have access to a light at night.
Has anyone fitted a vehicle interior light that can be used whilst the vehicle is in motion?
Any advice on fitting one too?

thanks

Dave


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## al n sal (Dec 14, 2010)

there's a wealth of info on insallation of eletrics on here, sbmcc.co.uk  (anyone can visit, not just for self build owners)

routing the cable out of view I guess would be your hardest task.

al


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## Nosha (Dec 14, 2010)

I don't understand why the habitation gets shut off?? The 'rear' should be run off a lesiure battery, which if it runs flat still allows the engine battery to start it, then with the engine running the split charge relay kicks in and charges the 'rear' battery.

I could be wrong but it sounds like you are running off the engine battery, but again why isolate it when the engine starts??

I think you may have a relay wired the wrong way round. (The fridge will have it's own supply and own relay).


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## maingate (Dec 14, 2010)

You do not say what model van you have but it is normal on most vans for the power to be cut off to the rear hab lighting. Only the fridge and gets 12 volt power.

What you can do is either plug into your cigar lighter and run a temporary feed to a light.

or

Take a feed direct from the leisure battery to a new light fitted somewhere convenient. make sure you fit a fuse as close as possible to the battery. You will need an on/off switch as well.

or

Buy an LED light that runs off AA batteries and mount that.


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## Firefox (Dec 14, 2010)

The habitation electrics normally get shut off. The alternator can produce as much as 16V + so I think the reason is stop fuses from blowing or protect components that aren't so tolerant of a slightly higher voltage.

But if you want to fit a light or a socket just follow Maingate's advice. Don't forget a fuse. You can fit an inline fuse to protect that circuit. Say 10 Amp wiring and a 5 Amp fuse.


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## Deleted member 775 (Dec 15, 2010)

all the electrics work in our van when runnig .you can have the lights on whilst driving on a night, we have a compas drifter 1983 model. i would imagine it is very inconvenient if you are carrying passengers on a night and they cannot have the lights on. is there a switch on the zig unit that will allow you to turn  the habitation electrics on or off


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## NicknClair (Dec 15, 2010)

Hi,

The NCC written in the so called "Caravan/Motorhome rules and regulations), that 12v has to be issolated whilst in motion!! Sargent consumer box installations on Autotrail's, Swift's, Bessacarr's, Autocruise's etc etc, have a relay system which issolates any aux equipment in the rear. To issolate (like I found) is a nightmare on my Kontiki, as certain items stop working such as the step retract when starting the engine and the Fridge on 12V.
In the end, I simply ran an seperate 12v socket and converted one of the lights over to perminent 12v, much easier and faster to do.


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## al n sal (Dec 15, 2010)

I'm definatelt not a electronics engineer or anything close, I'm sure i read somewhere that they like to have a relay in the domestic wiring to turn the hab elecs when engine running, to stop any chance of static elec, or build up of power around the wires interferring with the vehicle elec brain or safety features. something like tht  anyway,

but I could be wrong

al


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## Deleted member 775 (Dec 15, 2010)

cannot see a problem with the electronic engine management  as your running lights are on at night and engine management  are sheilded ,  and consider a car you can have the rear lights on inside  at night  ,the only stipulation about interior lighting is no interior light should be shown in front of the drivers eyesight .


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## jezport (Dec 16, 2010)

I think it is just British vans that have this feature, as both my last van (French0 and my current on (German) have working habitational 12v whenever you want them.


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## Tbear (Dec 16, 2010)

We have a locker with no light so I just stuck a battery powered LED to the cealing and it has worked well for months without a battery change. It did fall off once so mind the lads head


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## Deleted member 775 (Dec 16, 2010)

they are great ,and can be had for £1 for three we also use them and for reading on a night the head spot lights are good .wew used rechargeable batteries  even more economical


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## Beemer (Dec 17, 2010)

Battery lights certainly do seem like an ideal way to go, as they can be used at any time, even for a leisure battery failure.

I was wildcamping in south Wales at the weekend and met my brother in his campervan, when my heating stopped working in the evening because the leisure battery had only 6.5v.  I run the 'van engine for about 20 mins, which meant I could then run the diesel heating (it was a cold weekend), this gave me a temporary charge to maintain the heating for a while with the engine off, but could not chance using the lighting as well.
My brother came across to our 'van with one multi LED round light which cost him a pound and we placed it face down on the fly screen to give us plenty of light for the evening meal and the following drinks!!!
I think I will look into the type of battery lights available, and try to stick to LED, as they seem to run for longer on batteries.


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## maingate (Dec 17, 2010)

From Sunday, Aldi have a set of 3 small ones for £4.99.

If you subscribe to Aldi and Lidl to get their offers by email, there are a few useful things to get. So far, I have bought a good battery charger, an inside/outside thermometer, various LED lights and very good 18 year old Scotch Whisky.

Speaking of whisky, they have a bottle of 18 year old Glen Marnoch for £19.99 or a 12 year old Glen Marnoch for £16.99.


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## Deleted member 775 (Dec 18, 2010)

just try any pound land there only a quid for three and good quality .the only down side i find with led bulbs is if you do have a low battery they seem to dim  before the floresent tube lights do we have two 12 v led bulbs  in the spot lights in the rear and i have noticed this dont know if anyone else has .


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## rodvw (Dec 21, 2010)

It seems totally barmy to me to isolate the habitation power when the engine is running!


Rear passengers cannot use their electronic gadgets in 12v sockets.
My razor wouldn't recharge.
The Eberspacher wouldn't work.
The reading lights wouldn't work.
Etc. etc.

All additional 12v powered items like this are available in a coach, ambulance and other emergency vehicles not to mention strech limos etc. Why not in a motor home?
Surely it's just a case of keeping TV screens etc. out of the driver's sight to remain legal?

Rod


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## Beemer (Jan 5, 2011)

rodvw said:


> It seems totally barmy to me to isolate the habitation power when the engine is running!
> 
> 
> Rear passengers cannot use their electronic gadgets in 12v sockets.
> ...


 
Our diesel heating works when the engine is on or off.
I have since discovered (unfortunately) that the 12v fridge still consumes power when the engine has been turned off , I was under the impression that like a caravan the fridge switches off 12v when the engine is off, but I am reminded by reading the motorhome booklet that I should not run the fridge off 12v when the engine is not running as the battery could flatten in a couple of hours.....oops!


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## kenjones (Jan 5, 2011)

My Autosleeper works just like this. It's not a wiring fault.
The fridge and eberspatcher work when the engine is running but not the habitition circuit.
I agree that there are many very good led battery lights that would meet your needs or an extention from the cigar lighter to a 12v light - I use this method and it works well. How often do you need interior lights with the engine running?


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## rodvw (Jan 5, 2011)

To answer the fridge part of the above point.
Three way fridges (or simply gas fridges with a 12v operation) use a 12v heater element to mimic the gas burner when the gas is not available. This element is power hungry and should be wired via a similar (or additional conatct within) the split charge circuit that charges the leisure battery.
12v compressor fridges are totally different, they use very efficient 12v DC compressor motors and work just like your average domestic fridge. They work on the leisure battery circuit ALL OF THE TIME.

As for when do the camper lights etc. need to be used with the engine running?
Having fully belted seats in the rear it not unusual for our habitation area to be occupied by someone needing illumination whilst on the move. I also use the sockets for battery charging, inverter supply and my bluetooth GPS receiver (used with Autoroute on a laptop PC).

I also try never to use the vehicle 12v sockets for items that I could leave powered when we are parked thus I never risk flattening the starter battery.

Otherwise I simply cannot see a reason why they should not be live with the engine running if all items are wired correctly. Passing under overhead power lines is more likely to cause interferance with the various processors onboard than items within the vehicle.
I guess it's down to some person with an over active pen writing as many 'rules' as they can think of. That's not unusual for Britain is it?

Rod


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## maingate (Jan 5, 2011)

Most European vans still have 12 volt power while on the move, My Burstner does. There is an isolation switch if you do not need it. I find it handy to charge up my phone, razor and rechargeable batteries etc.

What I mean to do sometime is to run the 120 watt slow cooker through my inverter, so that we can have a cooked meal ready on arrival.


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