12s 7pin wiring

May 25, 2014
Visit site
Hi . Can any of you great people advise me. I have gone to wire in a new male 12s plug to my caravan a 2003 swift and noticed 1 thick white earth wire plus a thin white wire . Do they wire in to the same terminal? Also I have no blue wire I assume this correct and the black middle terminal has melted. Do you Know what may have caused this? Many Thanks in advance :)
Mar 14, 2005
Visit site
Generally in UK built caravan s the white wire is used for the 12v zero volts return wiring. But it would be helpful if you can get circuit diagram. These are sometimes published in the owners manual.

Any pin in the sockets that has melted the plastic means that pin has been carrying more current than it can handle. But it does not necessarily mean the circuit or an appliance is faulty, the problem can be just the quality of the pins mating with its socket has been poor and has caused a high resistance contact which may get hot with normal circuit currents.

The melted components should be replaced, and all the pins and sockets cleaned, and the pins which are split just widened a little bit to improve contact.
Jul 15, 2008
Visit site
.......the correct wiring for your caravan is explained in this help sheet at section 3.3

Click here

The thick white wire goes to pin 7 and the thinner white wire to pin 3.
See the notes on the help sheet at sections 3.3 and in particular at 3.5.17 regarding pin overheating.
The blue wire to pin 2 was omitted by some manufacturers.


Mar 14, 2005
Visit site
12s centre pin burn out is very common. Pin 7 is the fridge return and unless you keep checking the pins and opening the segments so that the pin fits tightly, it will happen again and again.

The reason it happens is that most people wiggle the plug as they push it into the socket, which as the centre pin is the longest it gets squashed and does not make a good contact.

The very best solution is to change the plug and socket to 13 pin setup which eliminates the problem completely.


Latest posts