12S socket

Mar 14, 2005
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I have read with interest the recent forums on 12s socket, recently after picking my caravan 04 Bailey up from service I turned on battery power to find no power (I was plugged into car at time) so I can only assume that my car 03 Octavia has incorrectly wired socket, it was okay with my 92 Monza. So presumably the car is not charging caravan battery whilst travelling, is not working fridge and can't be used in emergency if leisure battery dies. Can anyone advise if this is common problem? I don't remember my towbar fitter asking me what age van I towed and how can I rectify it? Thanks in anticipation
 
Mar 14, 2005
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If you had the car ignition on it would have energised the fridge circuit which is totally independent of the control panel.When the fridge circuit is live this works a habitation relay which cuts off the van interior circuits and diverts the power circuit (for use on site when van battery is flat etc) to charging from the car alternator.If you have the latest fridge with no warning light you can not readily see that its working on 12 V.I have fitted a flashing L E D across the 12V terminals so that I can see if its working.If you have the older (& better!) type of fridge with warning light and its not working it is probably because you do not have the dedicated fridge earth to the centre pin in the 12S socket.Hope that helps
 
Mar 14, 2005
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Ian, If the car engine was running the 12v to the van on pin 4 would not be available for lighting etc. When the engine is running the supply on pin 4 is switched to charge the battery by the'habitation' relay in the van. The relay is switched by the Fridge supply on pin 6 which has it's negative on pin 7.

You can check this by connecting the van to the car without it's engine running and switching on the internal lights. Start the engine and the lights should go out ( and the van battery should be receiving charge). There may be a slight delay dependant on the type of relay fitted in the car. The fridge supply should be available and if it has a DC light it should be illuminated.

If the car is wired for pre 99 standard you will have to connect the black wire on pin 7 of the socket to car chassis to get the fridge to work and operate the 'habitation relay'. The battery charge wire on pin 2 becomes redundant, but can be left in place, as long as the corresponding wire in the van cable is either not connected in the plug or teminated so that it cannot short out inside the van.

If you have any further problems or questions please come back.
 
Mar 14, 2005
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Ian

I had the same problem on my Toyota. If you are a member of the caravan club go to their site and print off a copy of the technical doc. It has excellent wiring diagrams. I fixed the problem in a few minutes. (on my back mind to run the new earth in)Theo
 
Apr 22, 2004
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The wiring for 12 s sockets changed in 1999 when an extra earth was introduced and I think there was 1 other change to the pin connections. The reason being that from 1999 on caravans were fitted with relays to switch over the power.
 
Mar 14, 2005
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The wiring for 12 s sockets changed in 1999 when an extra earth was introduced and I think there was 1 other change to the pin connections. The reason being that from 1999 on caravans were fitted with relays to switch over the power.
The changes to the 12S socket were actually adopted by some makers earlier than others.Our Bailey Pageant Magenta was fitted with the habitation relay in 1996. That is why I always say 1996ish. Just mentioning this to clarify the situation for Bailey owners.If you hook up to the car and turn the van interior lights on and then switch on the car ignition you have the habitation relay if the interior lights go out.
 
Mar 14, 2005
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The wiring for 12 s sockets changed in 1999 when an extra earth was introduced and I think there was 1 other change to the pin connections. The reason being that from 1999 on caravans were fitted with relays to switch over the power.
I keep posting this but its early dats and the gremlins abound.

The 12S system habitation change over relay was in fact in use by Bailey at least in 1996 which is why I always say 1996ish.

If when you plug the caravan into the car(ignition off) and switch the van interior lights on and then turn ON the car ignition the van lights go OUT then you have the habitation relay system.If they stay on even after you rev the engine a little then if all relays are working OK you do not have the habitation relay.
 

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