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Fundamentals and Best Practices in Wiring Harness Design: An Introductory Guide

This article will introduce the significance of wire harness design, how to carry out wire harness design, and the future trends of wire harness design.

The purpose and significance of wiring harness design

Wiring harness design serves a crucial role in the assembly of complex electrical systems, providing a systematic and efficient solution for organizing and connecting wires and cables within a variety of applications, from washing machine wire harness to wire harness for refrigerator.

The purpose of a wiring harness is to streamline the integration of numerous electrical components, ensuring a reliable and standardized connection that reduces the risk of errors, enhances durability, and facilitates ease of maintenance and repair.

By consolidating and protecting wires, a well-designed wiring harness contributes to the overall safety, performance, and functionality of electrical systems, ultimately saving time and resources in the manufacturing process while promoting consistency and reliability in the final product.

How to carry out wiring harness design?

Step 1 Determine the purpose of your wiring harness design

You need to know what equipment the wire harness you design will eventually be used on. Do you want to design a washing machine wire harness, dryer wire harness, refrigerator wire harness or other various wire harnesses. Once you've determined the type of application you want, you'll need to understand the electrical requirements.

Step 2 Create schematic diagram

Draw a schematic diagram to illustrate the electrical connections between components.

Use symbols to represent different components and lines to represent wires.

Step 3 Consider the usage environment of the wiring harness

Extreme weather conditions

For equipment that operates in extreme temperatures, such as heating equipment and outdoor lighting systems, the wiring harness must be designed to withstand temperature fluctuations.

Materials should be selected based on their ability to withstand thermal expansion and contraction without affecting electrical integrity.

Insulation and sheathing materials should be selected to remain flexible at low temperatures and resist degradation at high temperatures.

Moisture and drying properties

In humid environments, such as washing machines or outdoor applications, the wiring harness should be sealed and protected from water intrusion.

Moisture-resistant materials and connectors with proper seals prevent corrosion and ensure the electrical integrity of the harness.

Conversely, in dry environments, steps should be taken to prevent the build-up of static electricity that can damage sensitive electronic components within the harness.

Shock resistance and stress relief

This requires consideration of whether the wire harness will suffer large vibrations, such as washing machine wire harness, etc. The design of wire harnesses needs to carefully consider these factors to avoid the vibration environment affecting the use of the wire harness.

In addition, proper strain relief and secure wire bundling can effectively mitigate conductor fatigue and damage over time and ensure the safety of the equipment during use. The use of vibration-resistant materials and connectors is critical to ensuring the longevity and safety of the harness in such an environment.


Some applications, such as wire harnesses for refrigerators, may require a high degree of flexibility to adapt to changes in the environment.

Flexible materials and proper design considerations (such as the use of grommets and strain relief devices) can enhance a seat belt's ability to withstand repeated bending without damage.

Step 4 Understand the standards of wiring harnesses

Some standards you should be aware of include: ISO 9001 (International Organization for Standardization), RoHS (Restriction of Hazardous Substances), CE Marking, NEC (National Electrical Code), UL (Underwriters Laboratories), CSA (Compliance, Safety and Accountability), OSHA (Occupational Safety and Health Administration), VDE Electrical, Electronics and Information Technology.

Step 5 Choose the appropriate wire harness specifications

1. Current load

The selection of wire harness diameter should be determined according to the current load. Typically, the larger the current load, the larger the wire diameter required. If the wire diameter is too small, it will cause problems such as overheating of the wire harness, short circuit, and even cause a fire. Therefore, when determining the wire diameter, the appropriate wire diameter should be selected according to the size of the current load.

2. Voltage drop

The selection of wire harness diameter also needs to consider the voltage drop issue. There will be a certain voltage drop when wires transmit current, and excessive voltage drop will affect the normal operation of electronic equipment. Choosing a wire diameter that is too small will increase the resistance of the wire, resulting in an increase in voltage drop. Therefore, when selecting the wire diameter, the appropriate wire diameter should be selected according to the voltage drop requirements.

3. Wire harness length

Wire harness length is also one of the factors that affects wire diameter selection. Generally, the longer the harness length, the larger the required wire diameter. Because increasing the length of the wire bundle will increase the impedance of the wires, resulting in increased current loss. Therefore, when selecting the wire diameter, the appropriate wire diameter should be determined based on the length of the wire harness.

Step 6 Choose the appropriate wire harness material

Select specifications and materials for wires, cables, connectors, and other materials based on the environment in which your wiring harness will be used and what you will actually face, as well as compliance with standards.

Material selection for terminal blocks

The copper used in terminal materials (copper parts) is mainly brass and bronze (the hardness of brass is slightly lower than that of bronze), of which brass accounts for a larger proportion. In addition, different coatings can be selected according to different needs.

Selection of insulation sheath

Commonly used materials for sheath materials (plastic parts) include PA6, PA66, ABS, PBT, pp, etc. Flame retardant or reinforcing materials can be added to plastics according to actual conditions to achieve the purpose of reinforcement or flame retardancy, such as adding glass fiber reinforcement, etc.

Step 7 Draw the wiring harness diagram

Create detailed drawings that provide a visual representation of the wire harness, including information such as wire colors, labels, and connection points.


Include a title specifying the equipment or system to which the harness is intended.

Please note the version control revision number and date.

Component list:

Provides a list of all components connected by the harness.

Includes details such as sensors, actuators, control modules, etc.

Wire color and size:

Assign a different color to represent each wire in the harness.

Specify the size or gauge of each wire.


The connectors at both ends of the wire are clearly depicted.

Use standardized symbols for different types of connectors.


Label each wire with a unique identifier or alphanumeric code.

Provide a legend or legend that explains the meaning of each label.


Indicate where each wire connects to a component or other part of the system.

Use arrows to indicate the direction of signal flow.

Step 8 Prototype and Test

Build wire harness prototypes for testing and validation.

Verify that all connections are secure and that the wiring harness meets performance requirements.

Future trends in wire harness design

1. Combination of wire harness design and intelligent technology

The design of electrical wiring harnesses is gradually integrated with smart technology to achieve remote monitoring, diagnosis, and interaction with other smart home devices. This capability also makes wire harnesses likely to play a vital role in enabling devices to connect to the Internet of Things (IoT) and leverage artificial intelligence to improve performance, energy efficiency and user convenience.

In addition, the wiring harness also needs to be adaptable, with intelligent functions that can adapt to different conditions on its own to reduce maintenance needs and improve the efficiency of the equipment.

2. Faster data transfer speed

As the functions of modern devices continue to increase, multiple tasks are often required to be performed at the same time to meet our usage needs, which requires wiring harnesses with higher data transmission speeds to support advanced functions or multiple functions running at the same time.

3. Miniaturization and lightweight design

The trend of miniaturization and lightweighting is inevitable. Especially with the rapid development of small electronic equipments, there is an urgent need for compact wiring harnesses that are more energy-saving and can reduce space occupation.

4. Advanced and durable materials

Although the quality of wire harnesses has reached a high level, replacement is inevitable as time goes by or when they are frequently subjected to extreme environmental conditions. More and more wire harness manufacturers are using advanced materials or protective coatings to maintain the good performance of wire harnesses in harsh environments such as extreme climates, strong vibrations, and moisture.

As we become more and more aware of protecting the environment, producing greener and more environmentally friendly wire harnesses is also an important research direction for wire harness researchers.

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Originated Cable & Wire business in 1998, We has been dedicating itself to the manufacturing and exporting of high-quality Cable Assemblies, Wire Harnesses for lighting & Home Appliances, Worldwide Power Cord, Indoor & Outdoor Extension Cord, Electrical Wires, Plug Inserts or custom-made products.





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