Boat trailer wiring and all about Australian Trailer Wiring Codes
Australia has a standard wiring code on most trailer wiring and there is a standardized 7 pin system after 1988.
There are also many older 6 and 12 pin connectors in use that don’t always follow a code, so in most cases its trial and error when wiring up and repair connectors.
Make a regular check of trailer wiring, in particular look inside light fittings and the ends of wires into light fitting terminals are our checkpoint.
If the copper has become blackened it’s rotting out due to galvanic action of saltwater and will need replacing.
Many people assume its a non maintainable system but any electrical system that gets wet with saltwater every weekend is very prone to failure. Look at how you can improve the system with new LED type lights and ones that are encapsulated against water ingress
Usually the cable breaks with vibration when on the road and your lights start failing as they break, before you know it the highway patrol is stopping you and issuing you with a ticket for your faulty trailer wiring. So common I am sorry to say. Even worse is your brake lights don't work and someone hits you from behind and the bad news is its your fault, and a very large insurance payout not to mention the loss of you boat in serious cases.
This is unfortunate as it was probably okay when you checked before you left home, and its vibration that finally cost you dearly.
When trailer-wiring is being renewed use tinned copper wires if possible, it will save you a very hefty fine and it would have been cheaper to rewire the trailer in the first place.
7 Pin Connectors
1 – Yellow – Left hand Indicator Light
2 – Black – Reversing (backup) light
3 – White - Ground/earth
4 – Green - Right hand indicator light
5 – Blue - Service/trailer brakes
6 – Red - Stop (brake) light
7 – Brown - Tail, license, clearance light
12 Pin Connector
8 – Orange - Battery charger/winch
9 - Pink - Auxiliaries/battery feed
10 – White - Ground/earth
11 – Grey - Rear fog light
12 – Violet – Spare
All about boat trailer wiring is here