Our relay wire harness keeps power safe and steady. It is made
with thick copper wires that transmit power quickly and smoothly.
The outside cover is strong and keeps the cables safe.
Relays are small parts that work like power switches. They let a
small button control significant power safely and efficiently. Our
relay wire harness combines the relay, wires, and plugs into a
single, ready-to-use piece. The Fog Light Wiring Harness with
Switch and Relay is one of our top items. It has all you need to
set up bright, powerful fog lights fast. It connects to your car
battery through a fuse, then runs to the relay. When you press the
switch, the automotive relay clicks and gives complete power to
the lights. The thick wires carry strong power without heating up.
This keeps your switch cool and your lights bright with no
flicker. Even in rain, snow, or fog, your lights will stay strong
and clear.
A Dual Relay Wiring Harness can control two power lines with a
straightforward switch. This helps cars and trucks that use high
and low beams, as well as front and rear lights. It features two
relays built into a single setup, each with its own fuse. This
keeps power safe and even. If one side stops working, the other
still works fine. Each relay ensures power flows smoothly,
keeping your lights bright and steady. Thick copper wires and
robust relays make it suitable for long-distance drives and
high-power loads. It never overheats and continues to work even
under heavy use.
Headlight Conversion Wiring Harness (with Relay)
The Headlight Conversion Wiring Harness with Relay is made for
upgrading to HID or LED headlights. Many car wires can’t carry
enough power for new lights, so they flicker or go dim. This
harness addresses that issue by drawing power directly from the
battery through a thick wire with a built-in fuse. A small wire
connects to your old headlight line and signals the relay when
to activate. When you turn on your headlights, the relay sends
full, steady power to the bulbs. You get bright, clear light
every time. It also works seamlessly with DRL and CAN-BUS
systems. It’s easy to install, and you can do it yourself
without any tools.
Dual Relay Wiring Harness (Heavy Duty)
Our Dual Relay Wiring Harness (Heavy Duty) is designed for
demanding jobs and rugged use. It has two large relays that sit
side by side, each controlling a different light or system. One
can run daytime lights, while the other powers fog or beam
lights. Both work from one switch but stay safe on separate
lines. If one fails, the other keeps going. The short, thick
wires minimise power loss and ensure energy flows smoothly. The
relays have clear covers, making it easy to see inside and check
them at any time. This harness is excellent for off-road cars,
trucks, and custom builds. It also comes with a simple
installation guide that explains each step in clear,
easy-to-understand language, so anyone can install it.
Material Recommendations
Oxygen-Free Copper Conductor
We use oxygen-free copper (OFC) for all our wires. This type of
copper conducts electricity more efficiently, remains cleaner,
and lasts longer. It does not rust or lose its shine. OFC wires
handle high power without overheating, which means they are
safer and more efficient. They send steady, smooth power to your
lights, motors, or fans without drops or flickers. Due to this,
our relay wire harness kits are robust, long-lasting, and
suitable for all vehicles.
Plastic Granules
Our plugs and connectors are made from durable plastic granules,
including heat-resistant nylon. These materials can withstand
extremely high temperatures without melting or breaking. They
also resist oil, water, and coolant. Each plug is molded tightly
to keep out dust and moisture. This helps your relay wire
harness last longer, even in harsh or hot conditions. You can
trust it to withstand any weather conditions.
Transparent Five-Pin Relay
We also make transparent five-pin relays with clear covers so
you can see what’s happening inside. You can easily check if
it’s working or needs replacement. Some types even glow softly
when powered, helping you spot them in the dark. These relays
handle up to 80A and are great for checking and fixing your
electrical systems. They’re smart, safe, and very easy to use.
Corrugated Tubing
Every relay wire harness is covered in corrugated tubing, also
known as split-loom tubing. This soft but firm tube keeps wires
safe from cuts, heat, and dirt. The ridged shape lets it bend
easily without folding or cracking. It is simple to install and
keeps all wires in place. This tubing also protects against oil,
sunlight, and moisture, which helps your wires stay cool and
safe. It’s like a strong shield that guards your wiring from
harm for many years.
Ceramic Relay Socket
Our ceramic relay sockets are made for heavy-duty use. Ceramic
is robust and doesn’t melt, even at very high temperatures. It
also prevents short circuits and electrical leaks. The copper
parts are coated to prevent rust. This makes the sockets
long-lasting and safe, even in high-heat and vibration
environments. They are ideal for race cars, large trucks, and
off-road vehicles that require durable, reliable components.
Our Relay Wiring Harness Kits make wiring simple, safe, and fast. We
manufacture both ready-to-use and custom harnesses for all types of
power applications. Every relay wire harness comes fully built and
tested. You don’t have to cut, join, or solder any wires. Just plug
it in, tighten it, and it’s ready to go. If you require a
specialised solution, our expert team can design a custom harness
tailored to your exact needs and thoroughly test it to ensure it
functions perfectly.
Relay Wiring Harness
A relay wiring harness has all the key parts in one relay:
fuses, wires, and plugs. You don’t need to buy anything else. It
includes power wires with fuses, ground wires, and output wires.
All are wrapped in thick covers that keep them safe from heat
and bad weather. Most harnesses come with a switch as well. To
use it, connect one wire to the battery, one to your light, and
one to your trigger wire from the headlight. Press the switch,
and you’ll hear a click that means the relay is sending power
safely and smoothly.
Auxiliary Light Wiring Harness with Inline Switch and Relay
If you enjoy off-road driving or like to build cars that shine
bright at night, an Auxiliary Light Wiring Harness with Switch
and Relay is the best tool for you. It gives your lights a
strong, safe, and tidy way to get power. It features an
easy-to-use switch with a small, glowing light and a durable
relay that lasts a long time. You can put the switch anywhere
you like on the dashboard, beside your seat, or near your
steering wheel so it’s always easy to reach. With one simple
click, you can turn on fog lights, roof lights, or any extra
lights you have on your car.
Sometimes, one relay is not enough, especially when you need
more power for large lights or heavy tools. That’s where our
Dual Automotive Relays come in. This setup features two strong
relays and two fuses on a single, solid base. Each relay can
handle between 30A and 70A of current. This means you can power
two large lights, fans, or machines simultaneously without
worry. You can use both relays together or separately, depending
on your needs. It’s simple, safe, and ideal for vehicles that
require consistent power at all times.
Our harnesses are designed to fit cars, trucks, buses, and SUVs.
They power lights, horns, and fans. They make wiring simple,
clean, and safe for repairs or upgrades. We use the most
advanced and high-quality materials that are made for the exact
type of projects. The relay wire harness connects the power
source to the essential parts of the vehicle.
Boats and Off-road Vehicles
These harnesses handle dirt, mud, salt, and water easily. They
protect your lights and motors in all weather. The harnesses are
connected to all the material parts. The starts and the ends are
carefully sealed to resist the harmful elements. The harnesses
are designed to supply the power and the signals correctly.
Machines and Equipment
Cranes, robots, and industrial machinery use our harnesses to
obtain steady, safe power, preventing overheating. The materials
used in making the harnesses are durable and are best suited for
resisting tough weather. The machines and the equipment need the
exact type of power and signals for an accurate outcome.
Farming Equipment
Tractors and harvesters need tough wiring. Our harnesses remain
strong in high temperatures, dust, and vibration for extended
periods. In the farming sectors, these harnesses connect the
power and the signal parts to the control panel for an accurate
type of transfer.
Emergency Vehicles
Fire trucks, police cars, and ambulances rely on safe, steady
wiring. Our harnesses ensure that lights and sirens always
function correctly. The vehicle needs the perfect and exact type
of signals every time because of the safety process. And our
harnesses are designed for smooth performances.
Recreation and Custom Builds
Our harnesses are used for clean, safe wiring in RVs,
motorcycles, and golf carts. It’s perfect for recreation and
custom builds—like adding mood lights to a camping RV or
upgrading a golf cart’s features. With a relay wire harness kit,
adding new lights or devices is quick, secure, and easy for
everyone.
The Science of Safety: Tested for Every Volt & Pulse
ISO 7637-2 Transient Testing
We test the harness by simulating real power surges, including
spikes, dips, and battery breaks. We send strong power through the
wires repeatedly to see how they behave under stress. This is done
to ensure the wire cover and internal parts do not crack, melt, or
break over time. If the harness stays strong during these complex
tests, we know it can work safely in real cars, trucks, or
machines. The goal is to ensure it can withstand rapid power
changes, strong shocks, and rigorous use without failing.
Continuity and HiPot Tests
We check if power moves smoothly through each wire and plug. If
there is any break or weak point, we fix it or remove the wire.
Then we push a significant amount of power between the cables and
the ground to see if the cover can block the flow without leaking
or burning. Only wires that pass this test move to the next step.
This step is significant because it ensures that weak wires are
removed early, keeping the harness safe and strong.
Voltage Drop Check
We test how much power is lost when it travels through the wire
over a long distance. The lower the loss, the better the harness
works. We want the harness to stay cool, not hot. We use real
loads to make the test as realistic as possible. This ensures the
harness will last longer and function well, even with heavy use.
Vibration Stress Test
We place the harness on a machine that shakes it vigorously for
several hours. This copies how it feels on rough roads or in
machines that move a lot. The plugs and wires must not open, slip,
or break. If anything stops working, it fails the test. This step
helps ensure the harness can handle bumps, shakes, and turns
without any issues.
Environmental Cycling
We subject the harness to repeated exposure to heat, cold, water,
and salty air. This copies rain, sun, snow, and dust. The wires
and covers must stay soft, strong, and smooth. They must not
crack, rust, or get weak. We test it for a long time to ensure it
can work effectively in various conditions, including summer,
winter, rain, and dry air.
Functional Burn-In
We run power through the harness for many hours. We push it to its
limit. If any part gets weak, hot, or stops working, it fails.
After the test, we inspect the harness to ensure every part
remains in perfect condition. This test proves it can last a long
time, not just one day.
We place each wire concisely and straightforwardly. This saves
space and maintains strong power. Large cables are only used
where necessary, so the harness remains lightweight and easy to
handle. This design makes it easy to install, repair, and safe
to use for many years.
Modular Connectors
We utilize small plug blocks to consolidate multiple wires into
a single, neat plug. One plug can carry power, ground, and
signals. If something breaks, we only change one plug, not the
whole harness. This saves time, money, and makes work faster.
Fewer Parts
We smartly connect wires, using fewer parts. Fewer parts also
simplify installation and make troubleshooting faster when
issues arise later. One ground can be shared by many wires. One
relay can do more than one job. This cuts costs, saves space,
and makes the harness even stronger.
Flat Ribbon
When there are many wires, we bundle them flat and neatly. Our
Flat Ribbon design keeps wires flat for smooth small-space
passage. They pass through small spaces and stay tidy. We tie
them well so they do not move, hang, or break. This makes the
harness safe and clean to use.
Tell us about the type of car, truck, or machine you have.
Please let us know what you need, we listen to every detail to
ensure the relay wire harness fits your needs perfectly.
Plan and Quote
In one day, we make a simple drawing of the harness. You can
review it and request changes. We then provide you with a clear
price, with no hidden costs.
Sample and Test
We build a sample harness for you to test. You can check how it
fits and works. If anything needs to be changed during testing,
we fix it fast and make it better.
Build
After you are satisfied with the sample, we construct the final
relay wire harness using strong copper, durable plastic, and
safe covers. We scrutinise each piece to ensure it is perfect.
Ship and Help
We pack and ship the harness quickly with clear, easy-to-follow
steps for installation. Our team is always ready to help you if
you have any questions or need support.
Especially Designed & Built for Durability
Handles Heat
The harness can withstand both high and low temperatures. Even
in very hot engines, it will not melt, crack, or lose shape.
It keeps working safely.
Stops Vibration
Strong clamps and covers keep every wire and plug securely in
place. Even on rough roads or machines, nothing comes loose.
Blocks Interference
A metal cover blocks stray signals. This keeps the power
clean. It stops radio or computer problems from starting.
Keeps Water Out
Sealed plugs prevent water from entering. Rain, splashes, or
wet air cannot harm the wires inside. This keeps the harness
dry and safe.
Tough Outside
Sun, oil, dirt, or fuel will not hurt the cover. It remains
strong for years, even in harsh conditions.
These steps make the harness strong, safe, and ready for daily
hard work.
Trusted by Engineers, Validated by Performance
Many people who build cars, boats, and machines trust our harness.
It passes many complex tests to prove it is strong and safe.
Experts test it in labs with extreme conditions, including high
power, heat, and prolonged use. Companies trust it because it
works well and lasts a long time. Reports indicate that it works
effectively from day one and continues to function correctly for
years. Small shops and large fleets use it because they know it is
safe. We build it with care and skill so it lasts a long time.
QL-Custom Technology Ltd. is a trusted maker of Relay Wire Harness.
We have made strong and safe relay wire harnesses for more than 20
years. We control every step to maintain high quality. Our
innovative design and clear steps make your work easy. You can order
any size, length, or plug type. We use only strong, safe, and
long-lasting materials. Our team is here to plan, build, and support
you every step of the way. For safe, strong, and trusted harnesses,
choose QL-Custom Technology.
I added this fog light harness to my Jeep, and it made my
lights so much brighter and stopped the flicker. The wires are
thick, easy to move, and feel really strong. It only took me a
few minutes to install, and now my lights work great in all
weather.
Rajesh Kumar
I needed a harness for my off-road lights, and the team helped
me pick the perfect one. The wires and relays are tough, and
it still works great even after long, muddy rides. Great
quality and super easy setup.
Michael Chen
The support team was awesome! They helped me find the right
harness for my bike. The pre-wired setup was easy I only
needed a screwdriver. It works amazing and looks neat too.
Jessica Brown
I use large LED bars on my truck, and this harness works
perfectly. It handles heat, rain, and dirt with no problem. My
lights are bright and steady every time I drive.
David Martinez
Got a winch harness for my SUV. It’s super strong and
waterproof. I’ve used it many times in heavy rain, and it
still works perfectly. Very happy with it.
Liam O’Connor
This company makes great harnesses. The wires were clearly
labeled, the parts were strong, and I set it up in about 10
minutes. It works great and looks clean.
