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HomeTips & GuidesCar Wire Harness Designer: 10 Basics That You Should Know Before Designing a Car Wire Harness

Car Wire Harness Designer: 10 Basics That You Should Know Before Designing a Car Wire Harness

About Car Wire Harness Designer: While everything is now moving to automation, it needs a wire harness to perform its basic functions. In that matter, you have to design the harness according to the project you are working on.

For cars, the requirements are different. And so will your choices in the entire car wire harness design journey. 

In this article, we will dive into the details of 10 small aspects car wire harness designers need to know before putting their hands into car wire harness manufacturing. Let’s dig in.

Table of Contents


Again, first and foremost, car wire harness designers have to be clear about the purpose and application area of the wire harness. For example, a wire harness for a toaster may not serve anything in a big machine and may cause it to fail.

Similarly, an engine harness may not give any good to a simple lightning circuit of the car, although they will be applied in the same body.

So, the wiring material and design choice becomes more specific when the application area is clear. Here, you will also need to ask questions to yourself that. 

  • Do we need vibration-resistant material?
  • Or is there any extreme temperature the wires might be enduring, etc?

Wire Selection

Now that the main thought process is complete, you will start doing real work. You can take the following guidance to choose the wires.

Wire Specifications

Wire specifications refer to the gauge and the wire size you need, determining the current carrying capacity and flow amount per second. If the electrical requirement is high for the specific part of the car, you will need a wire with a higher gauge. 

Moreover, you will consider the length of the wire as well. You can use a shorter wire to reduce resistance and energy dissipation if the longer wire is unnecessary. 

Environmental Conditions

Before choosing a wire, you also need to look into the conditions under which the wire will work. If the wire has to work under extreme temperatures, you will need the one with a thicker outer covering.

However, a simple wire may work fine if the temperature is normal and there is no outdoor problem.

Mechanical Properties

Performance also increases when you are not bending the wires more often. Twisting the wires frequently may lead to abrasions on the cable’s inner conductor, reducing its current carrying capacity and offering more resistance.

While looking into every possible aspect, along with relevant standards for the car wire harness, you will ultimately find the type of wire you need.

Wire Connection

Different wire connectors

Caption: Different wire connectors

Wire connectors matter, too. The type of connection medium car wire harness designers choose will help create a circuit with less EMI

While selecting the connectors, remember that the wires will affect the connector’s performance. So, select the connector according to the wire you are using.

Moreover, consider the space limitations and choose the connector that will be easy to adjust and maintain.

Termination Type

As we are talking about the connectors, it is worth mentioning that termination type matters, too. So, choose quality connectors and clamping devices that can serve the best connection possible.

Go with standardization

Standard connectors are common in use; thus, you can fix them anywhere. On the other hand, if you go with the new connectors, it will be difficult to adjust with most wiring circuits. 

Also, you will have to read the whole documentation before using it, and you may not find any expert if any problem arises. So, it’s better to stick with the basic connectors.


Now that you have selected the components, it’s time to arrange them into the harness. While doing that, remember that accessibility and positioning is the key.

The design should be easy to maintain and repair when any issue arises. Also, it should be less entangled so that the interference is minimal.

Also, segregate your wires according to the voltage, function and signal type. Ensure that the wires are going to the correct device type.

Strain Relief

Wire harness designing in cars has to have the strain relief aspect or the vibrations will lose or repeatedly break the wires. 

Add strain relief components like cable ties, clamps, or grommets. Again, the choice will depend on the area of the car where you will install the harness. 

Also, apply these components where the wires go outside the wire harness. These points are usually prone to damage, and thus, they need special attention.

The material also matters, so choose the one that can endure the outer environmental conditions and chemical resistance.

Wire-Harness Diagram

Caption: Wiring harness, an example

A wire harness diagram helps you get things right from the initial step. 

As you have figured out the components, drawing the figure by hand will most likely lead to errors.

On the other hand, using computer-aided software will 

  • Check the flow of current, voltage drops and other circuit components’ behavior. Hence, the chance of errors will be less with time. 
  • Identify potential issues: the right software will help you see the cause and effect of using different components and types of connections. With it, the accuracy level will be much higher, and you will easily meet the standards. Moreover, the interference and limitations can also be pictured effectively.
  • Compile a circuit quickly. Moreover, with the rise in AI, some may help you generate a custom circuit without any work. 
  • Maintain the integrity of the design: Installing the wire harness in tight areas is the main concern, as major issues start when you can’t bend the wires. However, with some software, you can see where the issues with bending will arise and where you have to work. 

Protective Covering

Wire harness should also be protected by any sleeving or sheath so that it has an extra layer of insulation. This protection will prevent any outer issue from reaching the wires and damaging them. Also, material considerations are an important aspect.

Different protective coverings range from spiral wrap heat-shrink tubes to pulled-on braided tubes.


Testing is the key to ensuring a safe wire harness. While some people think the testing is done at the end of manufacture, it’s not true. It is better to start testing once you have made the prototype, which will help you point out all the flaws in the design.

If not done as soon as possible, the test results may lead you back to square one while wasting all the resources and energy. Mainly, you will test the following features of your wiring system.

  • Resistance
  • Threshold, time-up limits
  • Intermittent links


Documentation is very important if other technicians and after-sales persons will be involved. Through the right guidance, they can handle and repair any problem in the harness that will arise after use.

Hence, compile a comprehensive document with all the material details, schematic design and connector details.


In the end, there are certain standards to which the harness should comply to be fit for use. These standards make the product safe for usage according to the country and location they will be applied.

While there are many standards, the IPC/WHMA-A-620 is an internationally accepted set of rules. So, if you introduce the product internationally, it’s better to use the guidelines of IEC, CEE or CENELEC.


Designing a car wire harness is not a problem, even if you are new to the industry. You just need to follow the proper guidelines and seek professional help if there is any issue. Cloom has a lot of material to dive into for your ease. Our experts have researched and compiled what’s best for you.

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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