The 7 Pin Plug is known in the industry as the 12 N type plugs, that are used for road lighting only.

This is currently the most popular plug used for towing as it does the lighting on most trailers and caravans.

This is slowly being replaced by the European 13 pin plug and will become less popular as the reverse light is introduced to new trailers between now and 2012 when it will be legal requirement.

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.

To wire a plug or socket the first thing to do is to disassemble the plug or socket, this is very simple as the centre part that the wires fasten into can then be removed giving easy access to the screws then fasten the wires to the relevant pins.

When assembling a plug always remember to slide any grommets and caps down the cables before you start to attach cables.

The table below this shows the pin numbers in the 7 pin plug the colour wire that should connect to the pin as the diagram above and then states the trailer light that the wire should power.

All pins are marked and it can only be assembled one way.