Wire Harness Manufacturing: Learn the Step-by-Step Process


Have you ever seen the back of the steering wheel of your car? Did you ever take a look at the airframe of the aircraft? What did you see? There must be a lot of wire harnesses that help in managing and fitting into a specified space. During the wire harness manufacturing process, engineers decide the type of wire required, and the designers must design the harness keeping the space limitations in mind. Also, the wire harness design must be such that it does not affect the transmission of electrical signals. How can they overcome these challenges in developing quality products? Let’s find out the answer.

Table of Contents

What is a Wire Harness?

You can call a wire harness a cable harness or a wiring assembly. It is an integrated and systematic arrangement of wires, cables, connectors, terminals, and other electronic components within an insulating layer. The wiring assembly helps in transmitting signals and electric power. In the assembly, cable ties, straps, electrical tape, conduit, cable lacing, or a combination of these elements keep the wires and cables in place. With wire assembly, connecting and installing wiring with significant components becomes easy as the wires integrate onto a single unit.

Wire Harness Assembly Benefits

There are multiple benefits of using Cable assemblies in electrical systems:

“Plug-in” installations

Take the vehicles, for example. Generally speaking, vehicles use considerable lengths of wires for their operation. With a wire harness assembly, it becomes easy to integrate wires and cables into a single apparatus. As a result, the manufacturing of vehicles becomes easy and quick as you need to drop in the harness for wire installation rather than putting all the wires individually.

High-quality wire harnesses

As the wires and cables are present within the harness in an assembly, the different individual components remain secure and safe from the effects of moisture, abrasions, and vibrations. Also, there is high space optimization. Further, there are lesser chances of electrical short as the wires are present in a non-flexible bundle and a flame-retardant sleeve.

Wire harness design and pre-production

The equipment’s geometric and electrical needs decide the wiring harness designs. Once the designers finalize the initial setup, they create a schematic for paperwork and a manufacturing assembly board for the wire harness. Designers use 3D imaging systems and 3D modeling packages to prevent workflow faults at this stage.

The assembly or pinboard is a full-size wire harness diagram showing all the components and locations. It serves as a workbench for manufacturers to manufacture harnesses. Manufacturers lay the reins on the panel with pegs during the wire harness assembly process, ensuring that saddles have the exact dimensions.

What Your Contract Manufacturer (CM) Needs for the Wire Harness Manufacturing Process

You specify specific dimensions when contacting a contract manufacturer for wiring harness manufacturing. You can give this information simply through hand-drawn notes or complex 3D CAD models. The more accurate and detailed the report, the fewer problems on the assembly floor.

Here are some design specifications that can help your contract manufacturer in building wiring harnesses:

  • Detailed images of connectors showing pin locations
  • List of wires specifying wire colors, connector pin-outs, and nets
  • Bill of materials with their part numbers
  • Test specifications of finished harness
  • Drawing of complete assembly with assembly instructions, label locations, and tolerances

Further, it is also essential to give generic specifications to the wires, such as 600V or 300V, instead of using a specific UL code. With this information, your CM gets the flexibility to use components that work best for manufacturing wire harnesses and also which are best in terms of cost and availability. If you use specific UL-coded wires, it might be difficult for the manufacturer to find such cables and will be expensive too.

Colorful Wire set for assembling electrical appliances

Caption: Colorful Wire set for assembling electrical appliances

Wire Harness Manufacturing Process: Step by Step

After receiving your design specifications, your contract manufacturer begins their Wire Harness Manufacturing.

Design review

Firstly, your contract manufacturer will inspect the bill of materials and other documents to see if everything is in place. Along with this, they will also evaluate the specific parts to see if they are the best in terms of performance, cost, and availability. If unsatisfied, they will look for some replacements.

Materials preparation

After finalizing the bill of materials, the contract manufacturer will purchase all the materials and the components required for the production and testing of the harness.

Assembly documentation

During procurement, the CM will create assembly documentation for the manufacturing floor according to your input. It will have test procedures, assembly steps, and images and illustrations.

Inbound inspection

Manufacturers need to inspect the wires and other components from different suppliers before the assembly process to ensure no defects in production. It is also essential to check the gauge of the wire and see if they are of the required gauge. Manufacturers also check connectors for any damage. Another important thing to note is the space in the wire terminals so that pins are not placed very close. It is always better for manufacturers to use a digital system and document all the information regarding the defects in the products.


A prototype brings designs to life. Manufacturers use various measurement and inspection tools at this stage to make sure that the prototype matches the CAD drawing. It will be scrapped and reworked if the manufacturers face any issues or fail to meet specific needs. Getting the correct prototype at this stage is crucial as it will save time and cost later.


Once the prototype inspection completes, it’s time for the wire harness production.

  • A wire-cutting machine will cut the cables individually based on prior measurements and markings during the assembly process.
  • Next, the wires are labeled and laid out for design matching.
  • Now, technicians strip the insulation at the wire ends. Manual production sometimes reveals core wires, and damaged wires and insulation can cause safety issues. Therefore, manufacturers use magnification to strip wires and inspect wires after stripping to check for any damages.
  • After the stripping, crimping is also an important step. If technicians fail to crimp wires to the required height, it may result in defective continuity or wire displacement. Crimping should be perfect, as extreme crimping can damage the cables, while poor crimping can make the wires lose and disconnected. No matter whether technicians crimp the wires manually or through machines, it is essential to examine the crimped wires through an inspection process to look for any defects.
  • After crimping, terminals and pins are fit manually to the wires. One can seal the wires through solder machines or can insert the wires directly into the terminals. As the wire harness and its components are getting smaller and smaller, the assembler must use a microscope to see the soldering and terminal attachment process to avoid any faults.
  • The wires are gathered into a harness to meet the design specifications.

Manufacturers use quality processes and inspection systems at each step to improve the final quality of the harness. And they have to be precise and accurate at this stage as it affects the company’s profits and quality reputation.


After the production of the wire harness, it must undergo electrical safety testing. The testing ensures that the wire harness functions correctly at the end. This final testing includes continuity, megohm, visual inspection, and pull tests. If required, manufacturers make final adjustments to make the wire harness perfectly functional.

Terminal crimped colorful electric wire

Caption: Terminal crimped colorful electric wire

The Dos and Don’ts When Installing Your Wiring Harness

Once the wiring harness is ready, manufacturers give you termination recommendations to attach the wires. Make sure you use those recommendations, such as stripped and tinned or stripped and bare. In addition, you must also use manufacturers’ recommended values for the torque values on fasteners.


Cloom provides a wide variety of standard wire harnesses for general use and custom assembly for a particular service. Our technicians can stripe your Teflon, PVC, nylon, or irradiated materials with either 1,2, or 3 stripes in the color of your choice. We can also twist, cut, or dye wire to meet the intended application requirements. We also offer labeling services with laser-printed sticky labels or heat shrink tubing. Following this, we also tie your products with tie wraps or zip ties as required and requested by you.

Our wire harness assembly process ranges from the prototype to the final packaging at competitive pricing.