Wire a 6-Way Trailer Plug Without Mirroring the Connections

A typical 6-way trailer connection carries ground, running lights, combined left turn/brake, combined right turn/brake, electric-brake controller output, and an auxiliary circuit. However, the colors and terminal positions are only starting points: some installations reverse the brake-output and auxiliary-power connections, so wire every terminal by verified function (etrailer’s typical 6-way wiring guidance).

Typical 6-pin round trailer plug diagram

Diagram: Layout published by Husky Trailers for a 6-way round trailer-side plug, viewed straight into the front mating face with the index at the top. This is a source-specific layout, not a universal terminal standard.

In the layout above, brown is at the top, yellow and green are at the upper left and right, white is the center contact, and blue and black are at the lower left and right. It applies only to the stated trailer-plug, front-face orientation. The arrangement and color assignments come from the convention published in Husky Trailers’ connector guide.

Use this function-first reference rather than treating color as proof:

Circuit function	Typical color	What it operates
Ground	White	Return path for trailer circuits
Tail/running/license lights	Brown	Marker, tail, and license lights
Left turn/brake	Yellow	Combined left signal and stop lamp
Right turn/brake	Green	Combined right signal and stop lamp
Electric-brake output	Blue	Output from the tow vehicle’s brake controller
Auxiliary	Black or red	Often 12-volt power; may have another assigned function

White, brown, yellow, green, and blue recur across many 6-way conventions. The auxiliary conductor varies more often and may be black or red. Do not transfer the physical positions in this diagram to another connector unless its shape, orientation, and terminal labels agree.

Confirm the connector side and viewing direction

The trailer end is the plug and the tow-vehicle end is the socket. Their corresponding contacts face one another when connected, so diagrams of the plug and socket can appear opposite even when both are correct.

The view also matters:

• A front or mating-face view looks into the contacts that engage the other connector.
• A rear or wire-side view looks at the terminals where conductors attach.
• Front and rear views of the same connector appear mirrored.

Never rotate or mirror a drawing silently to make it resemble the part in your hand. Establish the top from the keyway, notch, latch, or other index feature, and keep that feature in the position stated by the diagram.

Orientation check

Before using any 6-pin diagram, identify:

1. Shape: round, square, or rectangular
2. Side: trailer plug or vehicle socket
3. View: front mating face or rear wire terminals
4. Index: the notch, key, latch, or marker designated as the top

Molded-connector drawings may show the front face because the cable is permanently attached. Serviceable hardwired-connector drawings may instead show the rear screw terminals. Croft Trailer’s connector sheet explicitly distinguishes front views for molded connectors from rear views for hardwired versions, demonstrating why two valid diagrams may look reversed (Croft Trailer’s 6- and 7-way connector diagrams).

Inspect a serviceable connector for molded abbreviations:

• GD: ground
• TM: tail and marker lights
• LT: left stop/turn
• RT: right stop/turn
• S: electric brake
• A: auxiliary

Follow connector-specific function labels ahead of a generic color chart. Then confirm the completed mapping electrically because previous repairs or nonstandard upstream wiring can still produce unexpected behavior.

Do not wire by color alone

Wire color is a clue, not an identity test. White commonly indicates ground and blue commonly indicates brake-controller output, but a familiar color does not prove what a conductor does.

Pay particular attention to the brake and auxiliary circuits. Some 6-way applications reverse the positions normally associated with the black battery-power connection and blue brake-output connection. A position copied from the wrong diagram could therefore place constant power on the brake circuit.

The sixth circuit is not guaranteed to be an always-hot supply. Depending on the trailer and harness, it may provide:

• constant 12-volt auxiliary power;
• support for a trailer battery or accessory;
• reverse-light power; or
• another model-specific auxiliary function.

Before removing an old connector, photograph its front, rear, index feature, wire colors, and terminal markings. Label each conductor by verified function, not just color. If both connectors have function markings, transfer ground to ground, tail to tail, brake output to brake output, and so forth—never by apparent clock position alone.

For an unlabeled trailer harness:

1. Disconnect the tow vehicle and isolate any trailer battery or onboard power source.
2. Identify the ground conductor by tracing it to the frame or designated return wiring.
3. Trace lighting wires to the corresponding lamp assemblies where accessible.
4. Trace the brake conductor toward the brake-magnet wiring.
5. Trace the remaining conductor to a battery, accessory, reverse lamps, or another destination.
6. If physical tracing is inconclusive, test the circuit with suitable equipment and record the result before making a connection.

Replacement guidance likewise recommends using old terminal labels when available and tracing or testing each circuit when labels are absent (etrailer’s 6-way-to-7-way replacement guidance).

Record the actual installation as you work:

Position from declared view	Wire color and terminal marking	Measured or traced behavior	Verified function
Top/index
Upper left
Upper right
Center
Lower left
Lower right

Write the declared view above the worksheet—for example, “trailer plug, front mating face, index up.”

Verify all six circuits before assembly

Begin with power disconnected. Open the connector and inspect for damaged insulation, corrosion, overheated plastic, loose screws, weak crimps, broken strands, and stray copper that could bridge adjacent terminals. Repair damaged wiring before enclosing it in a new connector. Guidance for this connector layout also calls for disconnecting power, checking the ground, securing and protecting the harness, and testing the functions before towing (Husky Trailers’ installation and testing guide).

Verify ground first. Where the trailer uses its frame as part of the return path, check continuity between the designated ground terminal and clean frame metal. If the trailer uses dedicated return conductors instead, follow that wiring design rather than assuming every circuit grounds through the frame.

Next, test the tow-vehicle socket with a multimeter or suitable circuit tester. Fix the connector index in one orientation and activate one function at a time:

1. Running lights
2. Left turn signal, followed by brake input
3. Right turn signal, followed by brake input
4. Brake-controller or manual-controller command
5. The intended auxiliary or sixth-circuit function

Observed behavior	Likely circuit
Steady voltage under the tested vehicle state	Possible always-hot auxiliary feed; confirm its intended use
Pulses with the left signal and responds to braking	Left turn/brake
Pulses with the right signal and responds to braking	Right turn/brake
Voltage appears with the running lights	Tail/running lights
Output responds to the brake controller	Electric-brake output

Brake-controller output should respond to controller or brake input instead of behaving like an ordinary constant-power feed.

Write down every result before attaching wires permanently.

Connect, protect, and test the plug

After every conductor has a verified function:

1. Disconnect all power. Unplug the trailer and isolate any onboard battery or other source that could energize the harness.
2. Fit the housing components first. Slide the cable through the backshell, cover, gland, spring, or strain relief before terminating the wires when required by the connector.
3. Prepare each conductor. Remove only enough insulation for the terminal, without nicking strands or leaving excess bare copper.
4. Connect by function. Attach each verified conductor to the corresponding molded label or connector-specific documented terminal.
5. Inspect the terminations. Tighten or crimp them as required and confirm that no loose strands can reach an adjacent contact.
6. Confirm the ground path. Where frame grounding is part of the design, secure the connection to clean bare metal.
7. Close and support the assembly. Install the cover or loom and secure the cable so it cannot drag, chafe, or pull on the terminals.
8. Apply compatible corrosion protection. Do not use grease or another product as a substitute for a sound crimp, tight terminal, intact seal, or correct circuit assignment.

After assembly, connect the trailer and observe the trailer itself while testing running lights, left turn/brake, right turn/brake, electric-brake response, ground integrity, and the intended auxiliary function.

Round versus square connectors—and common fault clues

Six-way connectors come in round, square, and rectangular forms. A terminal position on a round connector should not be assumed to perform the same function on a square or rectangular connector.

In one published convention, the round 6-way uses black for 12-volt auxiliary power, while the square version uses red. Square connectors are also associated with some popup-camper applications, but model-specific documentation or testing remains necessary (Lippert’s trailer wiring guide).

Symptom	First checks
Left and right signals are crossed	Confirm the viewing side and check for swapped left/right circuits
Nothing works	Verify ground, connector seating, and tow-vehicle output
Brakes receive constant voltage	Check for swapped brake and auxiliary terminals
No auxiliary output	Test the vehicle socket and the circuit supplying that terminal
Functions are intermittent	Inspect for corrosion, abrasion, loose terminals, and cable strain

For a 6-way-to-7-way conversion, map the existing six conductors to the new connector by verified function. Identify the unmatched seventh terminal separately.

Before towing, apply one rule: identify the connector and viewing side, wire every terminal by verified function, and test all six circuits. If the colors, molded labels, and generic diagram disagree, stop and rely on measured function or connector-specific documentation rather than the color convention.