This page is only provided to satisfy curiosity needs. If you need to check these colour codes, you may not have the prior knowledge needed to safely complete this complex wiring task. The diagrams do not indicate certain requirements including indicator relays (used to prevent trailer load affecting indicator flash rate,) beepers used as trailer turn indicator warnings and fog-light switching circuits. I advise that this page should not be used! I accept no liability for any problems that may be caused by ignoring this advice.

Car 7-Pin Black (Also known as 12N)
Many vehicles and trailers in the UK use this popular connector. It allows all the main road lights to operate but it does not connect the reversing light, permanent power or refridgerator supplies. In the UK, these connections are made using a second connector. Normally, the road lights operate via a black socket and the accessories use a grey socket. Although both sockets look very similar, it is not possible to accidentally plug incompatable plugs into either socket. The pins can be labelled L, 54G, 31, R, 58R, 54, 58L but this is often simplified using the alternative labels of 1, 2, 3, 4, 5, 6, 7
	1 (L)	Yellow Wire	Left Indicator
	2 (54G)	Blue Wire	Officially Rear Fog Light. Often disconnected,sometimes +ve power,some sockets disconnect cars rear fog lights when in use.
	3 (31)	White Wire	Vehicle Earth usually -ve (Sometimes this wire is thicker than the others)
	4 (R)	Green Wire	Right hand indicator
	5 (58R)	Brown Wire	Right hand tail lamp
	6 (54)	Red Wire	Brake Lights
	7 (58L)	Black Wire	Left hand tail lamp
Car 7-Pin Grey (Also known as 12N)
This is used as an accessories socket. There should also be a 7-pin black socket (described above) to supply the trailer road lights. The pins can be labelled L, 54G, 31, R, 58R, 54, 58L but this is often simplified using the alternative labels of 1, 2, 3, 4, 5, 6, 7
	1 (L)	Yellow Wire	Reversing Light (can link to trailer brakes)
	2 (54G)	Blue Wire	Rarely used
	3 (31)	White Wire	Vehicle Earth usually -ve (Sometimes this wire is thicker than the others)
	4 (R)	Green Wire	Permanent power (usually +ve), can be used for internal caravan lights etc.
	5 (58R)	Brown Wire	Rarely used
	6 (54)	Red Wire	High drain power (usually +ve) This only supplies power when the engine is running.(To stop high drain items e.g. Fridges, draining the car battery)
	7 (58L)	Black Wire	Second earth connection (usually negative)
13-Pin EU (or post 2009 UK) Socket (also knows as 13N)
This socket, popular in mainland Europe should not be confused with the various pre 2009 UK sockets which accept either the 7-Pin black plug or patented 13/14 pin customised plugs. (Many new UK caravans made after 2009 have this wiring but it is rare in the UK before 2008.) There are many variations in the wiring colours and I have only indicated some popular choices.
	1	Yellow Wire	Reversing Light (can link to trailer brakes)
	2	Blue Wire	Rarely used
	3	White Wire	Vehicle Earth usually -ve (Sometimes this wire is thicker than the others)
	4	Green Wire	Permanent power (usually +ve), can be used for internal caravan lights etc.
	5	Brown Wire	Rarely used
	6	Red Wire	High drain power (usually +ve) This only supplies power when the engine is running.(To stop high drain items e.g. Fridges, draining the car battery)
	7	Black Wire	Second earth connection (usually negative)
	8	Pink Wire or Yellow or orange or Other colour	Reversing Light (may affect trailer brakes)
	9	Purple Wire or Orange or Green or brown and blue or Other colour	Permanent Power (usually +ve)
	10	Grey Wire or Blue or Brown and Red or Other colour	High Drain Power (usually +ve) This only supplies power when the engine is running.(To stop high drain items e.g. Fridges, draining the car battery)
	11	Clear Wire or Black/White or Red or Blue/White or Other colour	Another Earth (usually -ve) intended as return wire for pin 10
	12	Buff Wire or Blue/White or Brown or buff or Other colour	Rarely used, intended for use within an alarm system or sensor device
	13	Black/White Wire or Red/White or Red or White/Green or black/red or Other colour	Another Earth (usually -ve) intended as return wire for pin 9
Lorry (24V electrics) ISO-1185 Connector (also known as 24N)
This wiring is sometimes found on lorries with 24V electrics - don't confuse it with the 12V car electrics unless you want a big repair bill!
	1	White Wire	Earth (usually -ve)
	2	Black Wire	Left hand tail/side lights
	3	Yellow Wire	Left hand indicators
	4	Red Wire	Brake lights
	5	Green Wire	Right hand indicators
	6	Brown Wire	Right hand tail/side lights
	7	Blue Wire	TRL control (often unused)
Lorry (24V electrics) ISO-3731 connector (Also known as 24S)
This is used as an accessories socket. There should also be a 7-pin lighting socket (described above)
	1	White Wire	Earth (usually -ve)
	2	Black Wire	ABS Warning System
	3	Yellow Wire	Reversing lamps and reversing audible warnings
	4	Red Wire	Permanent power (usually +ve)
	5	Green Wire	Rarely used
	6	Brown Wire	Power supply to the ABS system (usually +ve)
	7	Blue Wire	Rear fog lights