7 Pin Trailer Plugs & Sockets
Which 7 pin trailer plug do you need?
There are four 7 pin connectors in use in Australia, and they are not interchangeable. Three of them share the same pin assignment, and one does not.
7 pin flat is the most common, fitted to most boat, box and camper trailers. 7 pin small round is about the diameter of a 10c coin and 7 pin large round about a 20c, both keyed, and both wired identically to the flat. 7 pin heavy duty round is about a 50c coin with an oversized earth pin, is used on rigs over 3.5 tonnes, and follows a different standard: earth sits on pin 1 instead of pin 3, stop lights on pin 4 instead of pin 6, and there is no electric brake pin at all.
Pin positions on the heavy duty round look almost identical to the large round, so it is worth checking against our trailer plug wiring diagrams before you start stripping wires.
If your trailer is not 7 pin
- 12 pin plugs and sockets the caravan standard, where pins 1 to 7 match the 7 pin flat and five extra circuits sit above
- Anderson connectors for the charge line, since the lighting connector is not rated for sustained charging current
- All trailer plugs and sockets every connector type, plus adaptors for when the car and trailer do not match
Parts for the job
- Junction boxes to seal the joins at the trailer end
- Cable lugs for the earth and any heavy gauge terminations
- Split tube to protect the loom down the drawbar
- Grommets wherever the loom passes through steel
- Trailer tail lights the circuits this plug is feeding
- Adaptors and leads for 7 pin to 12 pin and round to flat
Guides
- Australian trailer plug wiring diagrams with pin numbers, circuits and cable colours
- Tow hitches and weight distribution for setting the coupling up properly
- Choosing a jockey wheel the other thing on the drawbar
