Caravan Electrics - Fridge

Jul 6, 2019
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Hi All,
After some advice regarding the electrics of our caravan and our tow vehicle. Our 2008 Ace Supreme has the fridge wired up directly to a constant live feed from the tow car battery. Should this feed be controlled by an ignition or voltage sensitive relay? I'm concerned that the direct feed will drain the car battery and it appears the caravan does not have a relay of some sort that protects the car battery from being drained. Any thoughts on this?

Also, when the caravan is hooked up to the tow vehicle, it appears that the habitation relay has kicked in as I'm unable to use any of the 12v lighting or water pump? My understanding was that this only occurs when the ignition is on or the car is running? Is that correct?
I'm unable to switch off the car battery connection via the caravan control panel when the car is connected to the caravan and power 12v from the caravan battery unless I've disconnected the caravan from the car.

Any help on this greatly appreciated!

Thanks
 
Mar 14, 2005
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Hello there,
Welcome to the forum.

The symptoms you describe are not normal, and as you suspect there should be some sort of control in your car that only supplies power to the caravan when the engine is running and the alternator has spare capacity to charge the caravan battery and supply the fridge.

Who ever fitted the towing electrics to the car did not follow the recommended methods, or perhaps the relay control in the car has developed a permanently closed fault. It needs sorting.
 
Jan 19, 2002
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As the Prof says there should be a relay within the car's wiring for the towbar that only provides 12v to the fridge when the alternator is providing charge, ie the engine is running. Otherwise you could for example stop for a lunch break, or try to drive off the ferry in france and find that the car battery was drained and you couldn't restart the car.

Otherwise for your second point it sounds that there may be a fault in the control panel which may be worth exploring.
 
May 7, 2012
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It does look as though whoever wired up the car did it wrongly or did not check it after fitting. If you paid a firm to do this then you need to take it back and get them to install a relay, or if one is fitted re[place it, as it must be faulty.
If the car came with it then take it back to the dealer who sold it or get a tow bar specialist to fit a relay.
 
Jun 23, 2019
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I've a similar question, how many connections are necessary on a tow bar for a caravan. I've been told 2 by one person (one for the lights as in a normal trailer) and one for the electrics of the caravan (Fridge, internal lights etc), another told me just one with proper wiring and a relay switch, as the caravan will only have one....? any guidance
 
Nov 16, 2015
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The two plug system 12n and 12 s were 7 pin connectors, but have been replace by the single 13 pin Which connect everything in one plug. You can get converters to go from one to the other.
 
Jun 23, 2019
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jayw said:
I've a similar question, how many connections are necessary on a tow bar for a caravan. I've been told 2 by one person (one for the lights as in a normal trailer) and one for the electrics of the caravan (Fridge, internal lights etc), another told me just one with proper wiring and a relay switch, as the caravan will only have one....? any guidance

Thanks for that. would you have any idea how old or young a caravan would be to definitely need only one plug?
 
Nov 16, 2015
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Not sure e about that, but this advert states about 2009, https://www.google.com/search?q=truma+vanmover&oq=truma+vanmover&aqs=chrome..69i57j69i60l2j33.9896j0j7&client=tablet-android-samsung&sourceid=chrome-mobile&ie=UTF-8

Thats not to say someone has not changed to a 13 pin themselfs. Does your plug push in and turn , or just push in. Count the number of pins inside.
 

Damian

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Mar 14, 2005
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If I remember correctly it was about the 2007 mark that the 13 pin single system was adopted by the UK makers, prior to that they used the two 7 pin system with a Black cable for the road lights and a grey cable for the reverse light, fridge (when connected to the car and engine running) and the battery charging circuits.

As for cars, many had just the single 7 pin socket and the extra socket had to be added afterwards, many of which were incorrectly wired !!!
 
Jun 23, 2019
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Thanks for all that, I've just found out from the tow bar fitter that if you have a 13pin (modern) on the car then you can get a 13-to-7 pin adapter for ordinary trailer work or a splitter (13-to2x7 pin for older caravans), both for about £10 each....
 
Oct 12, 2013
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That's what I used for my car to my trailer , an adaptor as my trailer used to have a seven-pin old plug but now have upgraded light board to LEDs so now 13 pin
 
Nov 11, 2009
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I converted my 2005 Bailey two connector arrangement to 13 pin DIN and the 2004 car also. No more bad connections, burnt pins etcand a far better technical solution. Plenty of videos on YouTube or web sites on how to do it. If your not confident it wouldn’t cost that much to have it done for you. The parts are cheap so it’s basically labour.
 
Sep 29, 2016
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jayw said:
Thanks for all that, I've just found out from the tow bar fitter that if you have a 13pin (modern) on the car then you can get a 13-to-7 pin adapter for ordinary trailer work or a splitter (13-to2x7 pin for older caravans), both for about £10 each....

Or for £3.00 delivered if you shop around ;)

e.g. https://www.ebay.co.uk/p/13-Pin-To7-Pin-Plug-Adapter-Car-Trailer-Truck-Caravan-Towbar-Socket-Converterru/23019949684?iid=401532598974&chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=401532598974&targetid=520884070959&device=c&adtype=pla&googleloc=9061002&poi=&campaignid=1782815658&adgroupid=70885935242&rlsatarget=pla-520884070959&abcId=1139126&merchantid=101449491&gclid=EAIaIQobChMInYek-fGv4wIVggvTCh0DgwZoEAkYASABEgJRmfD_BwE
 
Mar 14, 2005
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If you are happy about wiring converting a caravan with two leads to suit a car with only one 13 pins scocket is not all that difficult.
You make up a lead with a 13 pin plug on one end and then split the cables at the other end between a 12N and a 12s socket.
Then you connect this to the caravan back under the A frame faring , make sure all the connections are good and tested , then wrap up the 12n and 12s connections and secure inside the chassis members of the A frame using big cable ties. Ideally shrink wrap or otherwise protect the 12 s and 12nconnction beforesecuring in the A frame.
I've done this on two or three caravans in the past and actually found some plastic tubin that fitted over the 12 series connections, sealed the ends and never had any problem afterwards.
As has been said the quarter turn 13 pin connection is very much better than the 12 series and shoud be fine.
I did, however find that one new British made caravan had used non standard cable colours for their version of the 13 pin connection and had omitted the sealing on the plug - found this out the hard way in rural France when hitching up last day with long drive to ferry. Only Forum rules stop me naming maker but I=ve since changed caravans.
 
Mar 19, 2019
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A few people have said that power should only be provided at the socket when the engine is running and the alternator is spinning.

Is it normally that intelligent? I'd have thought it was just an ignition switched relay, i.e. if your ignition key is turned on, then the power is supplied, regardless of whether or not the engine is running and alternator spinning?

It's an important distinction, because a lot of people sit in services or waiting to board ferries, with the ignition key turned so they can listed to the radio. Can they flatten the car battery because they are also running the fridge?
 
Nov 11, 2009
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colinbal4 said:
A few people have said that power should only be provided at the socket when the engine is running and the alternator is spinning.

Is it normally that intelligent? I'd have thought it was just an ignition switched relay, i.e. if your ignition key is turned on, then the power is supplied, regardless of whether or not the engine is running and alternator spinning?

It's an important distinction, because a lot of people sit in services or waiting to board ferries, with the ignition key turned so they can listed to the radio. Can they flatten the car battery because they are also running the fridge?

Wouldn’t they normally be using the ignition switch in its auxiliary or first position hence not activating a relay. Sitting with full ignition on isn’t advised.
 
Sep 29, 2016
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jayw said:
https://www.amazon.co.uk/Trailer-Plug-Socket-MASO-Trailer-Converter-waterproof/dp/B07CGDJ7MF/ref=sr_1_22_sspa?crid=3S7GOBCTCWQQV&keywords=13pin+to+7+pin+twin+adaptor&qid=1563033233&s=gateway&sprefix=13pin%2Caps%2C148&sr=8-22-spons&psc=1

car 13 pin to 2 caravn 7 pin....handy!!!

Yes, very handy for those who need them, nice one, hadn't seen this before, thanks for sharing :)
 
Mar 19, 2019
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otherclive said:
colinbal4 said:
A few people have said that power should only be provided at the socket when the engine is running and the alternator is spinning.

Is it normally that intelligent? I'd have thought it was just an ignition switched relay, i.e. if your ignition key is turned on, then the power is supplied, regardless of whether or not the engine is running and alternator spinning?

It's an important distinction, because a lot of people sit in services or waiting to board ferries, with the ignition key turned so they can listed to the radio. Can they flatten the car battery because they are also running the fridge?

Wouldn’t they normally be using the ignition switch in its auxiliary or first position hence not activating a relay. Sitting with full ignition on isn’t advised.

Depends what ignition switched feed its wired into, for instance my 12v cigar sockets and stereo work in ignition position 1, but elec windows etc only work in position 2
 
Nov 11, 2009
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colinbal4 said:
otherclive said:
colinbal4 said:
A few people have said that power should only be provided at the socket when the engine is running and the alternator is spinning.

Is it normally that intelligent? I'd have thought it was just an ignition switched relay, i.e. if your ignition key is turned on, then the power is supplied, regardless of whether or not the engine is running and alternator spinning?

It's an important distinction, because a lot of people sit in services or waiting to board ferries, with the ignition key turned so they can listed to the radio. Can they flatten the car battery because they are also running the fridge?

Wouldn’t they normally be using the ignition switch in its auxiliary or first position hence not activating a relay. Sitting with full ignition on isn’t advised.

Depends what ignition switched feed its wired into, for instance my 12v cigar sockets and stereo work in ignition position 1, but elec windows etc only work in position 2

Thanks same as mine. Years since I had a 12 volt cigar :)
 
Jul 6, 2019
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Hi,
Sorry for the late reply! I'll return the car and believe I'll just need a relay to allow power to the fridge when the car is running. Hopefully that sorts out the issues.
Thanks
 
Jun 20, 2005
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otherclive said:
colinbal4 said:
otherclive said:
colinbal4 said:
A few people have said that power should only be provided at the socket when the engine is running and the alternator is spinning.

Is it normally that intelligent? I'd have thought it was just an ignition switched relay, i.e. if your ignition key is turned on, then the power is supplied, regardless of whether or not the engine is running and alternator spinning?

It's an important distinction, because a lot of people sit in services or waiting to board ferries, with the ignition key turned so they can listed to the radio. Can they flatten the car battery because they are also running the fridge?

Wouldn’t they normally be using the ignition switch in its auxiliary or first position hence not activating a relay. Sitting with full ignition on isn’t advised.

Depends what ignition switched feed its wired into, for instance my 12v cigar sockets and stereo work in ignition position 1, but elec windows etc only work in position 2

Thanks same as mine. Years since I had a 12 volt cigar :)
The connection to the 12v fridge circuit and 12v battery charging circuit is protected by a relay which only switches when the alternator on the car is turning and churning out a higher voltage in excess I think of 13.5 volts. It will not switch just on ignition or auxiliary. I assume it has been correctly fitted in the first place
 

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