At a Glance: Wire Harness Assemblies

• Combines multiple wires, cables, and terminations into a single organized assembly, simplifying OEM installation and reducing wiring complexity.
• Designed around the electrical and geometric requirements of the end equipment, wire harnesses help improve space utilization while protecting wiring from abrasion and vibration.
• Supports applications ranging from electronics and automotive systems to industrial equipment and household appliances, with configurations that can include dozens of wires and hundreds of components.

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Wire Harness Design

A wire harness, also referred to as a cable harness or wiring assembly, consists of single-conductor and/or multiconductor cables with terminations, connectors, sleeving, and other items to complete the build. A simple wire harness may contain only a few discrete components, while more complex harnesses can include dozens of wires and hundreds of components and terminations.

Epec Engineered Technologies supplies wire harnesses ranging from relatively simple configurations to highly complex assemblies containing numerous components, overmolds, and even integrated PCBAs. Our engineering team supports customers throughout the design and development process to help create an efficient harness solution that meets application requirements.

Common applications include:

• Electronics equipment
• Automotive systems
• Construction machinery
• Industrial equipment
• Washing machines and dryers
• Refrigerators
• Box builds
• Household appliances

By integrating multiple wires, cables, and subassemblies into a single harness, OEMs and installers can reduce installation complexity. The harness also helps protect wiring from abrasion and vibration while organizing conductors into a stable bundle that can improve space utilization within the finished product.

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Wire Harness Assembly Process

Once the wire harness design has been finalized, development begins with a schematic and a mechanical drawing used to generate manufacturing documentation and create the assembly board.

The assembly board, sometimes called a pin board or peg board, is a full-scale representation of the wire harness. It identifies component locations and serves as the primary work surface during assembly. These types of visual assembly aids help the operators lay out the entire cable and ensure the proper terminations are routed correctly. For high conductor count designs or bulky wire harnesses, the peg board can help make certain that each connector is positioned in space correctly and that the clocking orientation of each aligns with the mating connector.

Wire is supplied on large spools and is cut to the required lengths and then marked with flag labels or other means. After cutting, wires are stripped to expose the conductor and fitted with any necessary terminals or connector housings. The wires and components are then positioned on the pegboard and secured using appropriate fastening and bundling methods like tie wraps or zip ties. Additional wire bundles may be secured using straps, cable ties, cable lacing, sleeves, tapes, extruded-string weaves, or combinations of these methods to meet assembly requirements.

Typical assembly operations include:

• Installing wires and/or subassemblies on the assembly board
• Routing wires and/or subassemblies through required sleeves
• Applying wraps, ties, or tapes, especially at branch locations
• Crimping terminals onto wires, including applications where multiple wires enter a single terminal

Additional manufacturing activities may include:

• Cutting and identifying individual wires
• Partial insertion of terminated wires into connector housings
• Stripping, soldering or tinning wire ends
• Twisting wires
• Electrical tests to verify continuity and withstand voltage

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Manual Manufacturing and Automation Considerations

Despite continued interest in manufacturing automation, some types of wire harness production remain largely manual because of the variety and complexity of assembly operations involved.

For many applications, especially smaller production runs, manual assembly continues to be more economical than full automation. Certain pre-production activities and kitting operations can be partially automated, but many assembly processes still rely on skilled technicians to complete the final harness build.

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Wire Harness Testing

Electrical testing verifies the functionality of a completed wire or cable harness before shipment or installation.

Testing is commonly performed using a dedicated test fixture that is capable of performing the required electrical tests. Completed harnesses are connected to the tester and evaluated either individually or in multiple quantities to confirm that electrical performance requirements have been met.

With the dozens of electrical test options that could be performed, engineers and designers must define the exact test type and pass/fail criteria to help identify good from bad wire harnesses. Common electrical tests include continuity, hipot, and insulation resistance.

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Vertically Integrated Wire Harness Manufacturing

The wire harness manufacturing process begins with the extrusion of a single conductor jacketed wire. Multiple wires can then be bundled together to create a multiconductor cable assembly. Spooled wire may be stored until the remaining assembly components are prepared and ready for kitting.

Epec supports the various other steps within wire harness manufacturing that include overmolding, assembly of off-the-shelf items, and installation of labels, heat shrink, and other sleeving materials.

Through vertically integrated manufacturing processes, wire harness assemblies are produced with a focus on electrical performance and installation efficiency while supporting the requirements of custom applications.

Watch our cable assembly video as we review the steps in building a custom cable harness. The first step is to extrude a single conductor jacketed wire and then bundle it with other wires to form a multiconductor cable. Spooled wire can be stored until the rest of the assembly is ready to kit.

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Frequently Asked Questions

Quick Links

• What is a wire harness?
• How does a wire harness differ from a cable assembly?
• Why are wire harnesses used?
• What industries use wire harness assemblies?
• How are wire harnesses manufactured?
• Why are many wire harnesses still assembled by hand?
• How is a wire harness tested?

What is a wire harness?

A wire harness is a grouping of wires, cables, or subassemblies used to transmit electrical power or signals. It combines multiple components into a single organized assembly that simplifies installation in larger equipment.

How does a wire harness differ from a cable assembly?

Sometimes used interchangeably, the term wire harness assembly and cable assembly are essentially synonymous; however, some would argue that technically there are differences between the two.

Why are wire harnesses used?

Wire harnesses simplify the installation of complex wiring systems by consolidating multiple wires and components into a single assembly. They also help protect wiring from abrasion and vibration while improving organization and space utilization.

What industries use wire harness assemblies?

Wire harnesses are commonly used in electronics, automotive systems, construction machinery, industrial equipment, and household appliances such as washing machines, dryers, and refrigerators.

How are wire harnesses manufactured?

Manufacturing begins with a schematic, bill of materials, and any assembly fixtures and tools needed. Wires are cut, identified, stripped, terminated, positioned on the peg board, and secured using various bundling methods before final testing.

Why are many wire harnesses still assembled by hand?

Wire harness production involves numerous assembly processes that can be difficult to automate efficiently. For many applications, particularly smaller production volumes, manual assembly remains more cost-effective.

How is a wire harness tested?

Completed harnesses are tested using an electrical test fixture with the required instrumentation and mating connectors or probes. Assemblies can be tested individually or in multiple quantities to verify functionality.

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Need a Custom Wire Harness?

Epec designs and manufactures custom wire harness assemblies for OEM applications across a wide range of industries. With experience supporting harnesses that range from simple assemblies to designs containing dozens of wires and hundreds of components, our engineering team assists customers in developing wire harness solutions tailored to application-specific electrical and mechanical requirements.

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