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HomeTips & GuidesWhat Is a Wire Harness in a Car? – Everything You Need to Know

What Is a Wire Harness in a Car? – Everything You Need to Know

What Is a Wire Harness in a Car? A car has several sophisticated electrical systems that function normally and properly. While these electrical systems are independent, they must communicate with each other and get power from the same source. What aids this communication is a system of many long wires combined to make a wiring harness. With that said, let’s see what a wire harness is in a car, its types, and other vital harness information.

What Is a Wire Harness in a Car?

A car wire harness is a system of cables, wires, terminals, and connectors. As I mentioned above, they connect various car electrical systems, including headlights, airbags, climate controls, batteries, sensors, etc. This wiring harness relays electrical current, driver’s command information, and other communication to a car’s electrical components. Consequently, this communication enables you to effectively conduct functions such as steering, ventilation, braking, wipers, and headlighting.

Types of Wire Harnesses in a Car

As you may expect, several types of car wiring harnesses perform an independent function. Some of the main ones include:

  • Main harness: Is the primary cable system that powers most dashboard electronics such as headlights, signals, and more. Being the main system, it’s also the central unit where you can connect other sub-harnesses when they need additional power.
  • Floor harness: As the name suggests, this harness is located underneath your car. Its main function is to connect and power all electrical systems underneath your car for optimal performance when driving.
  • Interior harness: It connects and powers the electrical components inside your car cabin to the main system. These components include interior lights, power windows, audio systems, and locks.
  • Control harness: You install a control wiring harness to extend control or power to a more accessible location. Such a system is vital when installing aftermarket components that need more power than the already available. Additionally, such units ensure accessibility, clean routing, and protection from overloads.
  • Engine compartment wiring harness: The engine harness provides power from the battery to the alternator, fuel injector, ignition coils, starter motor, and spark plugs. This system also sends engine controlling and monitoring information from various sensors to the main computer. 
  • Air conditioning harness: Typically, the A/C wiring harness controls the temperatures in your car’s interior/cabin. For this reason, it transmits connects the AC, its engine, heater, and other electricals involved in car climate control.

Image of a car harness with connectors

Image of a car harness with connectors

How to Pick the Right Wiring Harness for Your Car

As you may expect, the right wiring harness depends on your car model and the types of harness you need. With that said, check the following factors to ensure the functionality and longevity of your chosen harness.

Check Fitment

In my experience, a standard connector comes with 12 circuits. However, you may get others with 18 or 24 circuits, depending on the vehicle and the needed harness. Therefore, I recommend carrying the one to the store to ensure you get a matching one.

Ensure Expandability

Getting an expandable harness ensures you can get more circuits in one board without buying an extra harness. Additionally, an expandable one does not experience many voltage losses.

Construction material

Here, you want a functional yet durable harness that can serve you efficiently for many years. As such, you want to ensure the inner wire is copper for efficient conductivity of your vehicle’s electrical load. For connectors, I recommend brass or coppers for longevity and avid aluminum. Also, check the insulation to ensure it’s thick enough to withstand temperatures, oils, and other harsh conditions.

Image of someone inspecting a wiring harness

Image of someone inspecting a wiring harness

How Is Wiring Harness Created?

Now that we know what wiring harness is and its types let’s see how manufacturers make it:

  • In the first steps, you get information about the functions of the electrical system that needs a harness. Your data may include its current loads and other unique features. You must also get information on the harness installation location and the type of connection and connectors required.
  • After gathering data on the specifications and functions of the electrical system, you now design a schematic of the vehicle’s electrical. You may do this by getting the required accessories and connecting them.
  • In this section, you now create a uniform design based on the schematic above and other multiple variations. A universal design helps cater to many customer needs while ensuring the process is not expensive and time-consuming.
  • Here, you make a complete and detailed 2D diagram that shows various aspects of the intended wiring harness. These aspects include the wire bundling designs, end connectors, and how to cover the bundles for wire security.
  • From the 2D diagram, you export and import the details to a 3D tool. Here, you also export the length of the harness, the connectors, and other details. This tool then utilizes this information to add other components such as sleeves, conduits, straps, cable ties, etc.
  • Once your design is complete, send the details to a manufacturing plant. Here, is where you have the real material gathering and wire cutting, plus the assembly of all the wire harnesses.

Testing cables after manufacturing

Testing cables after manufacturing

Benefits of Creating a Wiring Harness Using an EDA Tool?

While a wiring harness is a vital car component, its creation is time-consuming and demanding due to errors.

 However, many manufacturers have adopted electronic design automation (EDA) tools to streamline the process. 

This software ensures enhanced data consistency and design reuse for all manufactured harnesses. 

It also ensures data integrity, ensuring identical harnesses can integrate with your car systems without issues. 

Lastly, with this method, engineers can verify the functionality of the manufactured device before releasing it to the market.


With my research above, you know a lot about wire harnesses and how they work. Ensure that yours are updated and functional to avoid preventable, costly repairs.

Hi I am Christa, sales manager of Cloom.

I have extensive expertise and experience in wiring harnesses and I believe I can help you.

And we have a very professional technical team who can clearly understand the customer’s needs and give professional suggestions and solutions after receiving the drawings.

If you also have wiring harness needs, please send me the drawing so that we can give you our quote and start our business.

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