Six-way trailer plugs carry ground, tail, stop, turn, brake, and auxiliary circuits — this guide maps every wire and pin.
So before you crimp a single connector, grab a 6 wire trailer plug wiring diagram — the layouts look similar across brands, but the wire colors aren’t universal. Six pins carry six jobs: ground, tail and running lights, left stop/turn, right stop/turn, electric brakes, and 12V auxiliary power.
Six Functions, One Color Code
A 6-way trailer connector earns its place when a trailer needs electric brakes, a battery-charge line, or both, on top of the basic lighting.
| Circuit Function | Common Wire Color | Terminal Label |
|---|---|---|
| Ground (common return) | White | GD |
| Tail / running lights | Brown | TM |
| Left turn / stop | Yellow | LT |
| Right turn / stop | Green | RT |
| Electric brakes | Blue | S |
| 12V auxiliary / battery charge | Black or red | A |
Two warnings before you cut anything. Terminal labels differ between plug brands even when the functions match, and wire colors are a convention rather than a law — Croft Trailer’s chart, for example, shows red for auxiliary where other guides use black. The swap you’ll meet most often is the electric-brake and 12V auxiliary pair, which some trailer builders reverse on purpose, especially on horse trailers. CURT’s towing wiring guide labels the same six terminals GD, S, TM, LT, RT, and A, so read the mold marks on your plug shell instead of trusting memory.
How To Wire A 6-Way Trailer Plug
Six-way plugs ship either molded and sealed or as hardwired zinc die-cast units; both use the same function map, only the effort differs.
- Disconnect the tow vehicle’s power at the battery or connector so a stray strand can’t short against the frame.
- Mount the plug where the harness reaches without strain, then confirm the terminal labels molded into the plug shell.
- Strip each conductor and match it to the table above, pin by pin — ground, tail, left stop/turn, right stop/turn, brakes, and 12V auxiliary — before you crimp anything.
- Crimp or solder each connection and cover it with heat-shrink tubing so vibration can’t loosen it over time.
- Run the harness through split loom and secure it so it can’t rub against the frame or suspension.
- Test every pin with a multimeter or continuity tester before hooking up the trailer.
If the plug body is cracked or the pins are corroded, re-pinning an old connector rarely holds — see our tested roundup of 6-wire trailer plugs for replacements that seal up properly.
What Are The Most Common Wiring Mistakes?
Most 6-way failures trace back to four mistakes, and all four are avoidable in the first ten minutes of the job.
- Assuming the wire colors are universal — the same function appears under different colors on different brands, so always trust the terminal labels.
- Reversing the electric-brake and 12V auxiliary wires — some plugs have these swapped at the factory, and the warning shows up repeatedly in horse-trailer wiring.
- Skipping a solid ground — ground is the common return for every circuit, so a weak ground makes all six functions misbehave at once.
- Leaving the auxiliary circuit unprotected — add an inline fuse near the power source so a short can’t cook the whole harness.
When the trailer adds reverse lights or a separate brake-controller feed, the 6-way layout runs out of pins — that job belongs on a 7-way plug.
FAQs
What wires go where on a 6-wire trailer plug?
White runs to ground, brown to the tail and running lights, yellow to the left stop/turn circuit, green to the right stop/turn circuit, blue to the electric brakes, and black or red to the 12V auxiliary pin. Confirm the labels on your plug shell, because some manufacturers swap the brake and auxiliary positions.
Can I use a 6-way plug on a trailer with electric brakes?
Yes — the electric-brake circuit is one of the six standard functions and normally rides on the blue wire. Wire it to the brake controller’s output and verify it with a multimeter before towing. A 7-way plug only becomes necessary when the trailer adds circuits like reverse lights.
Why does my trailer’s brake wire show 12V power?
The most common cause is a swapped brake and auxiliary connection, which some plugs carry from the factory or a previous repair. Check the terminal labels on the plug shell and trace continuity from each pin to the trailer connector before assuming the brake controller is at fault.
References & Sources
- CURT. “Towing Electrical Wiring.” Identifies the six 6-way terminals GD, S, TM, LT, RT, and A.