Trailer Wire: Understanding the Basics

Trailer wire is a type of electrical wire that is designed to provide a stable electrical system to the lift system of the trailer and tow vehicle to allow the vehicle to work properly. Trailer wire is a stranded conductor made of copper wrapped with an outer layer of different colored PVC insulation that is abrasion resistant and flexible.
When wiring the trailer, you need to have a trailer wire harness, trailer wire connector, wiring tools, tape, and a circuit tester to ensure a proper and safe circuit. The different trailer wire color code represents the separate connections to the vehicle’s tail lights, brake lights, turn signals, etc.

trailer wire
trailer wire

Trailer Wire Gauge

The current carrying capacity of the vehicle and the wiring length determine the trailer wire gauge size. To ensure proper vehicle operation, trailer wire size should be selected with its wiring length in mind, and for longer trailer wires, 16 gauge trailer wire or 14 gauge trailer wire is recommended. Also keep in mind that the trailer wire will be thicker if the size number is small. The common trailer cable wire are 2 wire trailer wire, 4-way trailer wire and 7-way trailer wire.

Main Wire Gauge
Main Wire Gauge
Number of Wires
Number of Wires

Trailer Wire Gauge

The current carrying capacity of the vehicle and the wiring length determine the trailer wire gauge size. To ensure proper vehicle operation, trailer wire size should be selected with its wiring length in mind, and for longer trailer wires, 16 gauge trailer wire or 14 gauge trailer wire is recommended. Also keep in mind that the trailer wire will be thicker if the size number is small. The common trailer cable wire are 2 wire trailer wire, 4-way trailer wire and 7-way trailer wire.

Trvv cable
Main Wire Gauge :
Number of Wires :
Requires Quote
14 gauge 4 WAY TRAILER WIRES
Main Wire Gauge : 16 Gauge, 14 Gauge, 12 Gauge
Number of Wires : 4 Wire
Requires Quote
7 way trailer wire
Main Wire Gauge : 14 Gauge
Number of Wires : 7 wire
Requires Quote
Load More

Wire a trailer breakaway switch, people can follow these steps:
Step 1: Prepare the wiring tools, trailer wiring harness and connectors, etc;
Step 2: Find the breakaway switch on the trailer, usually located on the trailer bumper or frame, and then connect the wires to the breakaway switch;
Step 3: Use the tape to fix the trailer wires on the car bumper;
Step 4: Connect the other end of the trailer wire to the tow vehicle;
Step 5: Test the breakaway switch to see if it works properly.

Please be aware that when wiring a trailer, it’s crucial to follow the processes and guidelines.  For other special requirements, please consult ZWCABLE.

Below are the regular trailer wire color codes:

Red: Fused battery lead, connects to the trailer’s battery charger;
Brown: tail lights for connection to trailer and tow vehicle;
Yellow: left turn signal lights for connection of trailer and tow vehicle;
Green: for connecting the right turn signal of the trailer and tow vehicle;
Blue: brake lights for connecting the trailer and tow vehicle for the braking system;
White: connection to the grounding wire for safety on the road;
Black: provides backup lights for the trailer and connects to the tractor’s backup circuit.

The gauge required for trailer brakes is generally recommended to be 10 gauge-14 gauge. However, if a larger trailer is being used or if the wiring distance is longer, a 10-gauge trailer wire will be suggested. This will ensure that the trailer brakes are provided with sufficient electrical support for maximum effective braking. The above is just a guideline, and you need to ask the manufacturer or a professional electrician which gauge for trailer brakes to use.

Wire a trailer with 4 wire, follow the below steps can help you wire correctly:

Step 1: Purchase a 4-wire trailer cable with colors of green, yellow, brown and white. Then prepare the wiring tool;
Step 2: Connect the wires, green connects to the trailer’s left turn signal and brake lights, yellow connects to the right turn signal and brake lights, brown connects to the trailer’s taillights, and white belongs to the trailer’s earth wire for safety.
Step 3: Secure the wires on the car and then check to make sure the connections are intact and that the functions are working properly.
Lastly, the color code may vary in different regions, so please check the manual when wiring.

If you are in this situation, people can use these steps to Find the problem and solve it:

1. check for loose or damaged circuit connections between the trailer and the tow vehicle;
2. check for damaged bulbs in the turn signals and brake lights;
3. check for blown fuses in the trailer;
4. check whether the earth wire connection of the trailer is normal and needs to be cleaned and re-fixed.
5. check the trailer wires for signs of damage or loose connections;
6. Use a trailer wiring tester to diagnose problems with turn signals and brake lights;

If the preceding actions do not resolve the matter, then you need to consult a professional trailer technician to diagnose and repair.

Scroll to Top
Get in touch with us today and see how we can help you reach your goals!