Trailer wire harness - QL- Custom.com | Custom Over molding Cable Wire Harness Manufacturer

Our Trailer wire harness mfg history

QL-Custom Technology Limited design and manufacturing trailer wire harness and truck bed wire harness for the braking and lighting system since 2008 when we get a first order of a customer who comes from league city, Texas , a PL3 connector, we are very interesting on new harness design, prototypes, and mfg, when the custom send us a sample he mail us the sample we are waiting for that sample over 20days which shipping by U.S post, not shipping by Air, This sample was absolutely terrible - it had all sorts of issues like flash, shrinkage, you name it. We even suspected the material might be something like nylon or TPU, but after testing, it turned out it wasn't any special molding compound.For a plug design without pre-mold support, we kind of expected the quality wouldn't be great. But the customer asked us to improve it, and the result turned out excellent.Back then, trailer wiring harnesses were rarely made in China, so we were able to achieve around 30% profit. The customer was really satisfied with our product.

Our featured Trailer Wire Harness made in the past 10years

We truly love what we do, and over the past decade, our capabilities have gone far beyond just custom development. Today, we own more than 20 set of plug and connector molds.

Not only have we developed products like those shown below for our clients, but we are also committed to creating new products through imitation without infringement—ensuring full compatibility with major brands such as Philips, Grote, Peterson, and Hopkins.

Of course, if you prefer that we source and use connectors from these established brands, we also maintain well-developed cooperative relationships with them.

Universal Trailer harness for connecting your vehicle

This is for some aftermarket car compatible for using with trailers, dumping trailers or boats when you fishing boat driving out

Universal Molex connector for Trailer electrical applications

This universal connector is for most of car tail light distribute to the trailer electrical system to female mounted 7way trailer plugs

Tractor & Excavator harness - HDP connectors

If you need an ODM design for your vehicle , also available for us to make your tailored design

Trailer & Camper lighting pigtails

OEM & ODM a trailer lighting pigtail is also available use for mobile house and campers, Delphi/Molex/Deutsch connectors are popular to use with conduit loom

2,3,4,6,8positions flat molded trailer plugs

A flat trailer plugs molded can resist water when plug in and out, when you need to use a simple connections and easy to un-install when the trailer is parking.

Overmoled bullet 0.180’’ plug

Overmolded a male or female bullet plug is a popular design for the whole body harness use in a trailer lighting system

PL3 Overmolded plug

Are you still struggling with molding defects in special structures? We've already solved this problem.

Compatible to Grote & Peterson brand

Our connectors offer full compatibility with Grote & Peterson brands, avoid patent infringement, and significantly reduce your costs — up to 30% savings

PL10 Overmoled plug

The PL10 overmolded plug is a sealed electrical connector designed for harsh environments. It protects connections from moisture, dust, vibration, and strain, ensuring reliability in trailer lighting systems.

Why choose our trailer wire harness

1. Faster Delivery: Key materials are in stock, significantly reducing lead times.
2. Expert Design: Deep expertise in designing reliable trailer wiring systems.
3. Quality Assurance: Rigorous testing ensures full compliance with industry standards and your requirements.

Do you know the Processes in tractor-trailer wiring harness production ?

Tractor-trailer wiring harness production involves processes like cable cutting, terminal crimping, soldering, injection molding, braided sleeving, assembly, and testing to ensure durability and safety.. At QL-Custom, we use professional technique to assembling the harnesses:

Ultrasonic welding machine in house - For branch harness

Do you know the butt connector ?
Yes we are doing the branches not by crimping butt connectors, we are welding the conductor by ultrasonic welding machine. The butt connectors often use for temperary use during customers use for hook up another wires. But in trailer wire harness or truck bed body harness assembling we use ultrasonic welding for much more safe solutions.

Braiding Yarn in house - For the harness cover

Have you been seen a braiding on your harness except Conduit loom and PET braiding ?
Yes we have yarn braiding, this is very strong braiding for Tractor wire harness !
This yarn braiding for agriculture vehicle when they working in the farm and the vehicle is dirty, while high pressure water gun clean the vehicle the high water pressure would break the harness, this yarn is effective protect the harness !

Overmolding in house - For 2,3,4,5,7pin plug and the splitters

What you may not have seen are overmolded plugs — a process where terminals are first crimped and then entirely encapsulated via injection molding to form a complete, sealed unit resembling a pre-assembled connector. This method not only provides waterproof protection but also offers a key advantage: it allows outdated connectors no longer in production to be replaced. As long as the terminals are still available, overmolding can recreate a compatible plug even when the original housing is obsolete.

Trailer- Truck Wire Harness Materials Proposal

Durable, sealed trailer-truck wire harnesses using high-temperature cross-linked PVC, seamless overmolding, and corrosion-resistant terminals for extreme environments. Fully compliant with US safety standards.

TXL auto wire

Best for: TXL wire use for your vehicles

Thin wall, light weight. Handles up to 125°C. Rated 50V. Made from cross-linked polyethylene (XLPE) – way better than old PVC. Perfect for tight spaces in cars. Super common in automotive applications.

GXL auto wire

Best for: GXL wire for your trailer wire harness

Slightly thicker than TXL. Good for 125°C and 50V. Also XLPE – tough stuff. Used under the hood and in engine areas. Fits most automotive connectors. Reliable and widely accepted.

SXL auto wire

Do you know when you need SXL wire for your harness

Thickest insulation of the three. Same 125°C and 50V rating. Super durable XLPE material. Great for harsher environments like off-road or heavy-duty trucks. Meets all automotive specs.

Grease for terminals

Do you need grease for your terminals use ?

Applying grease on trailer wire harness terminals provides essential lubrication for easy mating, waterproofing and moisture resistance to prevent corrosion, and enhanced insulation protection for conductor integrity in harsh conditions.

TXL GXL SXL wire

Molding plastic

Conduit loom

Grease for terminals

What vehicles can use our Trailer Wire Harnesses

Our trailer wire harnesses are built tough for all kinds of rigs—logistics trailers, RVs, farm dump trucks, and construction haulers. At QL-Custom, we design durable, moisture-proof wiring that handles vibration, corrosion, and high temps to keep your fleet rolling reliably.

Logistic container wiring

We make wiring that stands up to long-haul abuse. QL-Custom designs harnesses with solid seals and high-temp insulation so your logistics trailers stay connected mile after mile, rain or shine. Use our safe harness are very reliable when you need to turn left, right or backward. A lighting correctly indication can keep person or other people read your attend clearly.

Utility trailer & Campers wiring

For RVs, we focus on safety and comfort. Our harnesses power lights, brakes, and living areas reliably. We design moisture-resistant circuits so your adventures don’t get cut short by electrical issues. Don't waste any more money and time on repair costs — what truly matters is your family's happy and love journey together.

Truck bed & Dumpers wiring

Farm life is rough—mud, dust, and shaking. QL-Custom builds harnesses with extra abrasion resistance and waterproof connectors to keep dump trucks and ag equipment running season after season. You can't afford a faulty indicator causing a collision during unloading, nor endless compensation disputes at the job site due to unclear signals. Trust our reliably designed turn signal wiring to prevent it.

Tractors & Construction Vehicle wiring

Heavy loads and rough sites need tough wiring. We design harnesses with enhanced strain relief and corrosion-resistant terminals so your construction and mining rigs don’t quit on the job. When you use our engineering vehicle wiring harness, the bright and clear indicator lights will catch the attention of children, showcasing your exceptional operating skills. This sparks an early interest in infrastructure in the next generation, inspiring them to build greater structures and create a brighter future—carrying forward your legacy of brilliance.

Trailer wiring harnesses connectors

At QL-Custom, we handle everything from common 2-8 pin plugs, PL3, PL10, and bullet connectors to legacy brands like Delphi, Deutsch, and Molex—even when they're discontinued.

We specialize in finding or creating high-compatibility alternatives that meet your performance needs without compromising reliability. Plus, with our deep custom development expertise, we solve even the trickiest connector matching challenges—so your trailers connect flawlessly, every time.

Trailer wiring harnesses terminals

With countless terminal options on the market, QL-Custom stands out by specializing in high-quality tin-plated terminals designed for performance and durability. Our terminals support a wide range of wire sizes—from #2 to #24—ensuring the perfect match for your current and voltage requirements.

A standout in trailer applications is our bullet connector series, available in popular sizes like 0.11", 0.15", and 0.18", offering both versatility and reliable connectivity. Whatever your harness needs, we deliver tailored solutions that won't let you down.

Deutsch connector for Trailer harness use

Tired of trailer connectors that corrode, shake loose, or fail in the rain? Deutsch connectors are the go-to for extreme reliability. We integrate them into custom harnesses because they're sealed against moisture, vibration-proof, and built to handle rough roads and heavy use. Whether you're running logistics, construction, or ag equipment, our Deutsch-equipped harnesses deliver solid connections season after season—no signal drops, no corrosion surprises. We source authentic Deutsch parts and assemble them to spec, so your trailers hook up easy and stay connected.

Pack Yard Connectors for Trailer Harness Use

Tough, simple, and built to last—that's Pack Yard. These connectors handle daily grind, moisture, and vibration without failing. And for high current and high voltage choices for your applications. Whether you're hooking up a flatbed, dump trailer, or equipment hauler, they give you a clean click-seal connection every time. No fuss, no corrosion, just solid signal and power transfer. We use them because they work—period.

Customer Reviews

This isn't my first harness, but it's sure gonna be my last for a long while. Hauling cross-country, I need reliability in rain, snow, and blistering heat. This harness has taken the abuse without a flicker. The connectors are robust, and the wiring is thick enough to handle real workload. A solid, no-nonsense product for professionals.

Liam Johnson

Peace of mind for our family adventures! Towing our camper through the mountains, the last thing I want to worry about is the lights failing. This harness is built tough and stays securely connected even on bumpy roads. It’s made hitching up and hitting the road a total breeze. Five stars for keeping our trips safe and stress-free!

James Davis

This thing lives a tough life on the farm—dust, mud, rain, you name it. Other harnesses have corroded and failed. This one is sealed up tight and keeps on working. The thick coating protects the wires from getting snagged or crushed. It's just built to last. Does exactly what it's supposed to do, no fuss.

Trailer & Truckbed wire harness

Our Trailer wire harness mfg history

Our featured Trailer Wire Harness made in the past 10years

Universal Trailer harness for connecting your vehicle

Universal Molex connector for Trailer electrical applications