Technical guide
Pin numbers, circuits and cable colours for every trailer connector used in Australia. Find your connector below, then wire straight off the diagram.
Telling the three round connectors apart
All three are round, all three are seven pin, and two of them are wired identically while the third is not. Size is the quickest way to identify them. Shown here at true relative scale.
7 Pin Flat
AS 4177.5-2004
How to spot it A flat black rectangular connector with seven pins in a single row. The most common trailer connector in Australia.
| Pin | Circuit | Cable colour |
|---|---|---|
| 1 | Left indicator | Yellow |
| 2 | Reverse lights | Black |
| 3 | Earth | White |
| 4 | Right indicator | Green |
| 5 | Electric brakes | Blue |
| 6 | Stop lights | Red |
| 7 | Tail lights and clearance markers | Brown |
12 Pin Flat
AS 4177.5-2004
How to spot it The same flat body as the 7 pin, with a second row of five pins above. Standard on caravans.
Pins 1 to 7 are identical to the 7 pin flat, so a 7 pin flat plug fits a 12 pin flat socket and works normally on those seven circuits.
| Pin | Circuit | Cable colour |
|---|---|---|
| 1 | Left indicator | Yellow |
| 2 | Reverse lights | Black |
| 3 | Earth | White |
| 4 | Right indicator | Green |
| 5 | Electric brakes | Blue |
| 6 | Stop lights | Red |
| 7 | Tail lights and clearance markers | Brown |
| 8 | Battery charger / winch | Orange |
| 9 | Auxiliary / battery lead | Pink |
| 10 | Earth | White |
| 11 | Rear fog light | Grey |
| 12 | Auxiliary | Violet |
Small 7 Pin Round
AS 2513-1982
How to spot it Round, keyed, and about the diameter of a 10c coin. There is a noticeably wider gap between pins 1 and 6. Some fitters rotate this connector so the yellow pin sits at the top, so go by the moulded pin numbers rather than by orientation.
Same pin numbers, circuits and colours as the 7 pin flat.
| Pin | Circuit | Cable colour |
|---|---|---|
| 1 | Left indicator | Yellow |
| 2 | Reverse lights | Black |
| 3 | Earth | White |
| 4 | Right indicator | Green |
| 5 | Electric brakes | Blue |
| 6 | Stop lights | Red |
| 7 | Tail lights and clearance markers | Brown |
Large 7 Pin Round
AS 2513-1982
How to spot it Round, keyed, and about the diameter of a 20c coin, with the six outer pins evenly spaced around a centre pin.
Same pin numbers, circuits and colours as the 7 pin flat.
| Pin | Circuit | Cable colour |
|---|---|---|
| 1 | Left indicator | Yellow |
| 2 | Reverse lights | Black |
| 3 | Earth | White |
| 4 | Right indicator | Green |
| 5 | Electric brakes | Blue |
| 6 | Stop lights | Red |
| 7 | Tail lights and clearance markers | Brown |
Heavy Duty 7 Pin Round
AS 4735-2003
How to spot it The largest of the round connectors, about the diameter of a 50c coin. It has no key. Instead, the oversized earth pin only lets it go in one way.
| Pin | Ref | Circuit | Cable colour |
|---|---|---|---|
| 1 | 31 | Earth | White |
| 2 | 58L | Left tail light and clearance markers | Black |
| 3 | L | Left indicator | Yellow |
| 4 | 54 | Stop lights | Red |
| 5 | R | Right indicator | Green |
| 6 | 58R | Right tail light and clearance markers | Brown |
| 7 | Centre | Reverse / auxiliary | Blue |
Less common connectors
The five above cover almost everything towed on Australian roads. If you are working on something else, these are the ones you are most likely to meet:
- 5 pin and 6 pin round share the round bodies above but use fewer circuits and a different pin order. They look close enough to a 7 pin round to catch you out.
- 13 pin and 15 pin Euro round are fitted to some imported vehicles and European caravans.
- 7 pin EBS round carries the electronic braking system data lines on heavy trailers, required under ADR 38/04.
Narva publish a full reference covering all of these, including cable cross sections and the EBS pinout. If you have a Narva connector in your hand, or you need one of the connectors above, it is the resource to go to: Narva trailer plug wiring guide.
Common questions
- Which trailer plug is the most common in Australia?
- The 7 pin flat is the most widely used connector for boat trailers, box trailers and camper trailers. The 12 pin flat is the usual choice for caravans, because it adds a battery charge line, an auxiliary line and a second earth.
- Can I plug a 7 pin flat into a 12 pin flat 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 simply do not get the five extra circuits.
- What does “cable entry view” mean?
- It means you are looking at the back of the connector, the side the wires enter, not the mating face. Every diagram on this page is drawn that way. If you read a diagram from the wrong side you will mirror the whole thing and swap your left and right indicators, so check which way round you are looking before you strip a single wire.
- Which wire is the electric brake wire?
- On the 7 pin flat, 12 pin flat, small round and large round it is pin 5, blue. The heavy duty round is the exception. It has no dedicated electric brake pin at all, and its blue wire is pin 7, reverse and auxiliary.
- Is the electric brake wire the same as the handbrake?
- No, and it is worth being clear about. Pin 5 feeds the electric brake magnets inside the trailer drums, and it is driven by the brake controller in your tow vehicle, so it is live every time you touch the brake pedal. A trailer handbrake is a mechanical lever with no wiring to the plug at all. The emergency circuit is different again: a breakaway system with its own battery that applies the brakes if the trailer comes off the tow ball. None of the three are the same thing.
- What is the difference between the small round and the large round?
- Size and nothing else that matters to you. The small round is about the diameter of a 10c coin, the large round about a 20c coin. Both are keyed, and both use the same pin numbers, circuits and cable colours. The small round is more commonly seen in Queensland and the large round in Victoria, though that is a trade convention rather than a rule, so always identify the connector in front of you.
- Why is the heavy duty round wired differently?
- It follows AS 4735-2003, which is aligned with the international truck standards SAE J560 and ISO 1185, rather than the AS 2513 and AS 4177.5 family the other connectors use. It is intended for vehicles and trailers over 3.5 tonnes. Earth sits on pin 1 instead of pin 3, stop lights on pin 4 instead of pin 6, and the left and right tail lights get their own pins.
- Do the pin numbers match the cable colours on every brand?
- The pin number and circuit assignment is set by the Australian Standard and does not change between brands. Cable colours in a pre-made trailer lead usually follow the same convention, but a lead that has been repaired or made up by hand may not. Always test each circuit before you rely on it.
Need the parts?
We stock trailer plugs, sockets and adaptors from Narva, KT Accessories, Hulk 4x4 and TAG, in flat, round and heavy duty.
7 pin plugs & sockets12 pin plugs & socketsAll trailer plugs & sockets
Always check with the manufacturer if you are unsure.
