Wiring diagram for a 12n tow bar socket and plug

The 12N connector on a car or towing vehicle is the most common socket on the of the car. On what is know as single electrics it is the only socket added. The reason for this is that a 12N powers the indicators, brake lights, fog lights and side lights. If you are planning to tow a caravan you will also want a 12S socket to provide power to the fridge and charge the caravan battery etc.

If you are installing a towbar yourself, need to check that the electrical sockets on your tow bar or caravan are wired up correctly then this page should help you check everything works ok and is wired up correctly. You will also find this helpful if you find that your 12n socket or plug (this is the socket that controls and powers the lights on the rear of your caravan or trailer) has been damages and needs replacing.

You can buy a replacement 12n socket or a 12n plug for just a few pounds, doing the job yourself will save you money compared to aksing your caravan dealer or local garage to do the work.

12n wiring colours Pin Colour What it does
1 Yellow Left indicator
2 Blue Auxiliary (e.g. Fog light or internal lights)
3 White Earth
4 Green Right indicator
5 Brown Right Tail Light
6 Red Brake / Stop Lights
7 Black Left Tail Light and Number Plate Lights


When connecting up a new socket or plug ensure that the wires are in good condition. Often, over time, moisture will get in the plugs and sockets and cause corrosion on the wires. These can cause poor connections resulting in the caravan lights not working at all or not how you would expect.

Its important that a relay is used for the indicators that activates a light on the dashboard or buzzer so that when the indicators are being used the driver is aware that they are working.

At the start of every journey or after a break take the time to check that all the lights on the caravan are working properly, it could save a nasty accident and / or a fine.