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The 7 Pin ‘S’ Type ( 12S ) trailer plug is used for supplying reverse lights and
gives auxiliary power to other systems such as fridges, internal lights and charging systems
This was replaced in 2008 by the 13 pin Euro plug on all new caravans
To view our range of 7 Pin 12S Plugs, Sockets, Extensions & Convertors: CLICK HERE
From ( 29th October 2012) all Newly Manufactured O2 Class trailers require a Reverse light
Many major manufactures have been fitting reverse lights and 13 pin plugs on O2 trailers for a few months before this date
The 7 pin ‘N’ type (12N) plug will still be used on O1 class trailers and many towbar fitters
will still offer the 7 pin Socket as the cheapest alternative
It is recommended that a split-charge relay should be wired into your ‘S’ type caravan wiring At a set voltage this relay will divert some of the power that usually charges your vehicles battery to the auxiliary systems in your caravan This is useful for charging auxiliary batteries and powering appliances like fridges and freezers while you are driving
Wiring Diagram for a 7 pin 12S plug
Below is a diagram of a 12S plug with coloured pins as they are wired
On the rear of the pins the numbers are marked in the plastic next to each pin
The pins usually have a small screw to retain the wire on the back
When assembling a plug always remember to slide any gromets and caps down the cables before you start to attach cables
Which colour wire goes where in a trailer plug
Following the Information below this shows the pin number in the 7 pin plug, the colour wire that should connect to the pin as the diagram above, and then states the function that the wire should power
| 7 pin 12S Trailer wiring Diagram | ||
| Pin No. | Wire colour | Trailer light Function |
| 1 | Yellow | Reversing Light |
| 2 | Blue | 12v ignition on (battery charging) |
| 3 | White | Earth for terminal 2 and 4 |
| 4 | Green | 12v Permanent (direct from battery) |
| 5 | Brown | Reversing sensors (usually spare) |
| 6 | Red | 12v Ignition On (fridge) |
| 7 | Black | Earth for terminal 6 |