Trailer Plugs & Sockets
Choosing the right trailer plug
Australia uses five trailer connectors, and the pin assignment for each is set by an Australian Standard rather than by the brand. That means the plug you need is decided by what is already fitted to your tow vehicle and trailer, not by preference. Match the socket on the car to the plug on the trailer, then check the pin numbers moulded into the housing before you wire anything.
If you are not sure which one you have in your hand, our trailer plug wiring diagrams guide has the pin numbers, circuits and cable colours for all five, including the heavy duty round, which is wired differently to everything else.
Shop by connector type
- 7 pin plugs and sockets for flat, small round and large round connectors, the most common fitment on boat, box and camper trailers
- 12 pin plugs and sockets the caravan standard, adding battery charge, auxiliary and a second earth to the 7 pin layout
- Anderson connectors for high current charging, fridges and dual battery systems, not for lighting circuits
What else you need to wire it up
- Junction boxes to keep the joins sealed and serviceable at the trailer end
- 6 B&S cable for charge lines and heavy current runs
- Cable lugs for battery and earth terminations
- Split tube to protect the loom where it runs along the drawbar
- Grommets to stop the loom chafing where it passes through steel
- Adaptors and leads for when the car and trailer do not match
Related to the same circuit
- Trailer tail lights for stop, tail and indicator lamps
- Clearance lights required on wider trailers and caravans
- Brake systems including controllers for electric trailer brakes
- Breakaway systems the separate emergency circuit with its own battery
- Accessory plugs and sockets for 12V outlets on the trailer or canopy
Guides worth reading
- Australian trailer plug wiring diagrams covering all five connectors pin by pin
- Installing a dual battery system the charge side of a caravan setup
- DC-DC charger guide how the trailer battery actually gets charged
- Tow hitches and weight distribution the mechanical half of the coupling
- Tyre pressure monitoring the other thing worth setting up before a big trip
Common questions
How do I know which trailer plug I have?
Go by shape and size first. The flat connectors are rectangular. Of the round ones, the small round is about the diameter of a 10c coin, the large round a 20c, and the heavy duty round a 50c with an oversized earth pin. The pin numbers are moulded into the housing.
Can I use a 7 pin plug in a 12 pin socket?
Yes. The 12 pin flat is an extension of the 7 pin flat, so a 7 pin flat plug fits a 12 pin flat socket and the first seven circuits work normally. You just do not get the extra five.
Do I need an Anderson plug as well?
If you are charging a trailer or caravan battery, usually yes. The lighting connector is not rated for sustained charging current, which is why caravans commonly run a trailer plug for the lights and a separate Anderson connector for the charge line.
