12N and 12S Caravan & Trailer Wiring Charts

12N shows standard trailer lights: indicators (yellow/green), brake (red), earth (white), side/marker/plate lights (brown/black). 12S adds supplementary circuits: reverse (yellow), battery feed/ignition/fridge positives (green/blue/red), plus earths (white/black) and optional reverse sensor (brown).

from Western Towing – www.westerntowing.co.uk

12N (Normal) Socket & Plug Wiring

Pin No.	Function	7 core wire colour
1	Left Hand Indicator	Yellow
2	Rear fog light(s)	Blue
3	Earth	White
4	Right Hand Indicator	Green
5	Right Hand Side lights, marker lights & number plate light	Brown
6	Brake lights	Red
7	Left Hand Side lights, marker lights & number plate light	Black

12S (Supplementary) Socket & Plug Wiring

Pin No.	Function	7 core wire colour
1	Reverse 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

About the Author: Chris Hood

Chris Hood is a Director of Western Towing, bringing over 23 years of hands-on experience in towbars, trailers, and towing solutions. Having worked directly with vehicles, customers, and installations throughout his career, Chris combines practical expertise with in-depth industry knowledge to deliver reliable, safe, and tailored towing solutions. His commitment to quality workmanship and customer service has helped establish Western Towing as a trusted name across the South West.