If you need to replace or rewire a 7 pin trailer plug, this quick guide will help. A 7 pin plug, also known as 12N, is used for basic trailer lighting including indicators, brake lights, tail lights and fog light. Watch the video below for the step by step process, then use the notes underneath as a quick reference.
Looking for an 8 pin plug instead? If your trailer uses the newer 8 pin setup, go to our 8 pin trailer plug wiring guide.
Watch: How to Wire a 7 Pin Trailer Plug
What a 7 pin trailer plug does
A 7 pin trailer plug is used for the standard road lighting functions needed for basic towing. It is commonly found on small trailers, light boards and older towing setups. Unlike 8 pin and 13 pin systems, it does not include a reverse light or additional 12V power feeds.
- Indicators
- Brake lights
- Tail lights
- Fog light
Buy a 7 pin plug Buy a 7 pin socket
Step by step: wiring a 7 pin trailer plug
The full process is shown in the video, but the basic approach is simple if you work carefully and follow the correct pin layout for your plug and trailer.
1) Open the plug and prepare the cable
Unscrew the plug body, slide the outer parts onto the cable first, and strip back the outer sheath carefully so the inner wires are exposed.
2) Strip the individual wires
Trim and strip each wire neatly so you have enough bare copper to make a secure connection without leaving too much exposed.
3) Match each wire to the correct terminal
Follow the 7 pin wiring layout carefully and connect each wire to the correct numbered terminal. Double check the pin positions before tightening everything down.
4) Secure the cable and reassemble the plug
Make sure the cable clamp grips the outer sheath properly, not just the inner wires. Once the wires are secure, reassemble the plug body.
5) Test all trailer lights
Before towing, plug the trailer in and test each lighting function to make sure everything is working correctly.
Common mistakes to avoid
- Forgetting to slide the plug housing onto the cable first. This is one of the easiest mistakes to make.
- Using the wrong pin layout. Always double check the numbered terminals before wiring.
- Loose terminal screws. Poor connections can cause intermittent lighting faults.
- Too much bare wire exposed. This increases the risk of shorts and unreliable electrics.
- Not testing the lights properly. Always check indicators, brake lights, tail lights and fog light before towing.
When is a 7 pin plug the right choice?
A 7 pin plug is often the right option for basic trailers and light boards that only need the standard road lighting functions. It is still widely used and remains a simple, effective choice for many older or straightforward towing setups.
If your trailer needs a reverse light, an 8 pin plug may be the better option. If you need more advanced auxiliary power, such as for caravans, a 13 pin setup is usually the better choice.
FAQs
Is a 7 pin trailer plug still legal in the UK?
Yes. A 7 pin plug is still legal for basic trailers and light boards where only the standard road lighting functions are required.
Does a 7 pin plug include reverse light?
No. A standard 7 pin plug does not include a reverse light connection.
What does 12N mean?
12N is the traditional name for the standard 7 pin lighting plug used on many older and simpler towing setups.
Can I wire a 7 pin plug myself?
Yes, if you are confident working carefully and using the correct pin layout. If you are unsure, it is safer to ask for help before towing.
Need help with trailer electrics?
If you are not sure which plug type you need, or you would like help with trailer electrics, plugs, sockets or towbar wiring, speak to the GT Towing team.
Contact GT Towing Towbar electrics and fitting
Read the full 7 pin, 8 pin and 13 pin guide or view wiring diagrams.