Premier Manufacturer
At Romtronic, we can design and customize all trailer harnesses, from forklift and semi-trailer harnesses to specialized harnesses for heavy trucks. The harness ensures durability in all weather conditions and reliability in any environment. We have what you need, available at your convenience, whether you’re seeking standard off-the-shelf units or completely custom harnesses.
Our Custom Trailer Wiring Harness Styles
Below are some personalized trailer-wiring harness products that we produce. For more pictures of our products, click here.
Why choose us for custom trailer wiring harnesses?
Choosing Romtronic for your custom trailer wiring harness means getting a product designed to handle extreme weather conditions. Whether your trucks operate in icy, slushy environments or scorching, dusty terrains, our harnesses are designed to ensure your equipment stays running smoothly. Our advanced braiding technology provides reliable control over every part of the electrical system, from lighting to braking. Additionally, our custom potting materials enhance durability, reducing replacement costs.
With our cutting-edge ERP system and detailed production documentation, Romtronic guarantees consistent, high-quality results. We’re proud to hold certifications such as ISO 9001:2015, ISO 14001:2015, ISO 45001:2018, and IATF 16949, ensuring adherence to top-tier standards. And with 24-hour online service, we’re ready to respond quickly to your inquiries, from drawings to orders.
Our Quality
At Romtronic, we produce high-quality custom trailer wiring harnesses. The technical quality of each cable component is verified through stringent electrical testing conducted by IPC/WHMA-A-620 standards (our quality control procedures are outlined in a separate document) and ISO requirements. We can assist you with ODM and OEM wiring harness orders, thanks to our multiple quality certifications and over 20 industry patents. Please let us know if you would like to receive our quality manual now.
Benefits of a trailer harness:
- Easy assembly: The trailer wiring harness features a standardized design, making it easy to connect to the vehicle’s original wiring without complicated settings or adjustments.
- Applicable to many types of vehicles: The trailer wiring harnesses can be used in cars, station wagons, trucks, and boat trailers, among others.
- Weather resistance: The trailer wiring harness is made of high-quality materials. It’s durable, and it can withstand the winter environment.
- The trailer wiring harness utilizes multifunctional capabilities, and various electrical devices of the vehicle need to be connected for different purposes, such as lights and brake system signal transmission, which require a comprehensive range of electrical support.
- High-performance power supply: The trailer wiring harness is designed to provide a consistent, high-power output, ensuring the regular operation of any connected accessories.
- Plug and play: Easy to set up and remove, the trailer wiring harness features a plug-and-play interface. The most crucial feature of this design is that it allows you to quickly connect or disconnect the bulb without the need for a standard electrical connection.
Common Trailer Wiring Harness Specifications and Applications
Trailer wiring harnesses can have various configurations based on the number of pins. Each pin serves a distinct purpose and connects the trailer’s electrical system to the trailer itself. Standard trailer wiring harnesses come in 4-pin, 7-pin, and extended versions—the big jump is to 13-pin.
1, 4-Pin Trailer Wire Harness: This is the most basic and commonly used trailer wiring harness. It provides essential electrical connections for the trailer’s brake lights, turn signals, and tail lights. The four pins correspond to the following functions:
- Pin 1: Ground (connects to vehicle chassis)
- Pin 2: Tail/marker light (rear light illumination)
- Pin 3: Left turn signal/brake light (activates left turn signal and brake light)
- Pin 4: Right turn signal/brake light (activates the right turn signal and brake light)
2, 77-Pin Trailer Wire Harness: Adds extra connectors and is standard on larger trailers and agons. The 7-pin harness provides the same features as the 4-pin harness with these additions:
- Pin 5: Electronic Brakes (sends a brake signal to the trailer’s electronic brakes)
- Pin 6: Reverse Lights (activates the trailer’s reverse lights)
- Pin 7: Auxiliary power (provides power to accessories such as interior lights, electric stabilizer, etc.)
3, 13-PIN Trailer Wire Harness: This 13-pin trailer harness is commonly used in Europe and other regions. It retains all the wiring harnesses of the 7-pin trailer wire harness but adds a few more. The 13-pin harness connections are as follows:
- Pins 1-8: Same as the 7-pin harness (ground, tail/marker lights, turn/brake lights, e-brake, reverse lights, auxiliary power)
- Pin 9: Reverse lights (another connection for reverse lights)
- Pins 10-13: Other functions such as auxiliary power, driving lights, refrigerator power, or trailer stability control.
It is worth noting that the function of each pin can vary depending on the wiring specifications used in your region. Please refer to your vehicle manual or wiring diagram before installing and connecting your trailer.
Frequently Asked Questions (FAQs)
Q1: What types of trailer wire harnesses do you manufacture?
We offer a wide range of trailer wire harnesses, including 4-pin, 5-pin, 6-pin, and 7-pin configurations for utility trailers, boat trailers, RVs, and agricultural equipment. Custom designs are also available based on your specific vehicle or application.
Q2: Can you customize trailer wire harnesses for different regions or standards?
Yes, we can manufacture wire harnesses that meet North American, European, or other regional electrical standards. Just share your specs or drawings, and we’ll deliver a compliant solution.
Q3: What materials do you use to ensure durability and weather resistance?
We use high-quality automotive-grade wires, PVC or TPE jackets, and waterproof connectors to ensure excellent resistance to abrasion, moisture, and extreme temperatures—ideal for outdoor and off-road environments.
Q4: Do you offer sample or prototype wire harnesses?
Absolutely. We can provide samples or prototypes for evaluation before moving into mass production. This ensures the final product meets your design and performance expectations.
Q5: What is your typical lead time for trailer harness production?
Lead times vary depending on order volume and complexity, but standard orders usually ship within 2–3 weeks. We also offer expedited options if needed.
Get in Touch for Custom Trailer Wire Harness Solutions
Romtronic provides high-quality, custom trailer wire harnesses tailored to meet the specific needs of utility trailers, boat trailers, RVs, agricultural trailers, and more. Whether you require 4-pin, 7-pin, waterproof, or multi-function trailer wiring, we have the experience and capability to deliver reliable solutions.
To request a quote, discuss your project, or get expert support, feel free to contact us through the form on this page or using the details below — our team will respond within 12 hours.
📧 Email: info@romtronic.com
📞 Phone: (+86) 199-2816-5824
Romtronic is your trusted partner for custom trailer wiring solutions, serving customers in over 80 countries worldwide.