Caravan 12S 7pin socket & plug wiring

 

This is the standard UK wiring of a the supplementary socket and plug otherwise known as 12S. There have been slight variations over the years as most newer caravans control the battery charging in the caravan rather than from the towing vehicle. The earth return is also a more recent addition as it used to be spare but since caravan fridges have got larger it was necessary to provide a separate earth return for the fridge. The diagram below shows the view from outside the vehicle socket (under the flap) and from inside the caravan plug.

12S supplementary Caravan wiring Diagram

 

Terminal Number Function 7 core wire colour
1
 Reversing Light
Yellow
2
 Positive Ignition key ON (Battery Charging)
Blue
3
 Earth
White
4
 Positive direct from battery
Green
5
 Reverse Sensor (Optional), usually spare
Brown
6
 Positive Ignition key ON (Fridge)
Red
7
 Earth return for Fridge (Terminal 6)
Black

 

The normal light socket or plug 12N diagram and wiring chart can be found here