HomeTips & GuidesWhat does the wire harness do in a car?

What does the wire harness do in a car?

We all use machines, such as automotive, in our everyday lives. Further, the importance of wiring harnesses can be seen in all electronics and automobile industries. And you may wonder: what does the wire harness do in a car? Let’s dive in!

What is a wiring harness in a car?

You can find wire harnesses everywhere, including every rocket, jet, and plane in the sky. You can also find them under the hood of every truck and car on the road.

Wire harnesses are also known as cable assemblies or cable harnesses. They describe a systematic set of wires or cables bundled together to form a single integrated unit. 

They are components of a car as they function similarly to the human body’s nerves and blood vessels.

Automotive wiring harnesses comprise sheaths, terminals, connectors, and other components surrounding the core of electrical wires.

What does a wiring harness do in a car?

We have compiled this article to help you know more about the functions of wire harnesses in a car.

Fulfill the primary functions of the vehicle.

Auto wiring harnesses are key to controlling electronic accessories by handling information and energy flow with the E/E system to perform:

  • Basic automotive functions, such as braking and steering
  • Secondary automotive functions like infotainment and ventilation.

For example, the engine wiring harness connects to various components that require electricity, such as alternators, batteries, and starters. 

The wiring harness begins at the engine compartment and connects to the fuse box, where the wires are branched to their different accessories and then return to the engine compartment.

Solenoids and sensors also have wiring harnesses to monitor and control major systems, such as the transmission, ignition, and fuel systems. 

These cable harnesses transmit information/data from the sensor to the electronic control unit (ECU), allowing instant adjustments. 

ECU connectivity problems that check engine lights and trigger warnings are not caused by the sensor’s failure but by a cable harness’s damage.

Provide a single, organized route.

An automotive wiring harness helps secure cables against the adverse effects of moisture, abrasion, and vibrations by holding multiple wires in a single non-flexible bundle.

 This protection reduces the risks of electrical short circuits and extends the lifespan of the wires.

Besides, auto cable harness bundles different cables according to their functions and destination points within the car. 

Therefore, a cable harness keeps the wiring system organized, which is crucial for the following reasons:

  • It contributes to a more efficient and safer car operation
  • Makes troubleshooting of electrical problems easier
  • Simplifies the installation process
An organized route wiring harness

An organized route wiring harness

4 reasons a cable harness of a vehicle can go bad

A vehicle cable harness can go bad because of the following reasons:

Poor designing

If you ever thought an automotive cable harness is a simple one-size-fits-all component, you were entirely wrong! 

If the wiring harnesses are not spread according to the application specs, they may fail to fit into the finished item.

When manufacturing vehicle wiring harnesses, manufacturers strip the ends of the wiring to join wires with the terminal. 

They also make cuttings on the wires according to the required length. If the manufacturer fails to work on it as expected, the resulting error can create blunders, such as:

  • Vague estimations
  • Helpless association with the cable harness chassis
  • Inappropriate wire formats
  • A piece of equipment getting lost or missed

The created errors can prevent the entire automotive cable harness from fitting seamlessly and appropriately inside the application

Defecting crimping or soldering

Crimping is a popular type of bond used to join cables to terminals. When crimping is not done as expected, it can lead to open circuits inside the component or a serious short circuit. 

So, whether utilizing a machine or hand-crimping, ensure the machine is set up correctly for the wire size you want to crimp.

However, crimps are more prone to overheating. Therefore,

soldering the wire to the terminal can form a more solid and grounded bond in applications that include movement or exposure to vibrations. However, a soldered joint can have problems,

especially if the soldering tip is not the correct size or if the temperature is excessively cold or excessively hot.

Degraded or low-quality material

Copper alloy is considered a much more ideal material for wiring and terminals than OEM-grade copper. 

This is because rehashed pressure causes OEM-grade copper to break or overheat.

Moreover, the overmolding material and defensive jacketing of an automotive cable harness must be viable with ecological factors, such as:

  • Extreme temperatures
  • Synthetics
  • Exposure to oil and lube, etc.

While over-molding is not immune to environmental conditions, it can quickly break, erode, soften, become fragile, and uncover the wires.

Incompatible components

To prevent an automotive cable harness from overheating, the size of the component must be compatible with the wattage and amps. 

However, using standard incandescent lights versus the present-day halogen can mess up compatibility. And inexperienced specialists can easily miss this.

Auto wiring harness repairs

Generally, an automotive cable harness requires the following components:

  • Wires or cables
  • Terminals
  • Splices
  • Backshells
  • Shrink tubings
  • Contacts
  • Braid or string tie. You can use these to hold the bundled cable harnesses together.

The probability that you will need to replace the cable harness is very low. For instance, it is common for a wiring harness to last the whole lifetime of the car you installed it in. 

If there is an issue, you may only replace a part of the auto cable harness with an individual part.

However, you may need to replace the entire cable harness if the damage is extensive, such as melted wires. 

Also, we recommend replacing instead of repairing more sensitive cable harness systems, such as airbags.

The cost of buying and installing a new cable harness varies greatly depending on the location and size of the wire harness. 

An automotive wiring repair

An automotive wiring repair


An automotive wire harness keeps the electrical wires organized and easily managed and protects them from damage. 

It also ensures an uninterrupted flow of electricity, allowing the car to function as it should. 

To avoid disaster and malfunction, checking the internals regularly and fixing any wiring issues in the vehicle is crucial.

However, opt for the appropriate specialized harness if you’re working on a specific subsystem like the engine or chassis. 

Cloom Tech manufactures custom wiring harnesses and cable assemblies to suit every vehicle’s needs.

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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