Vehicle Wiring Harness: A Detailed Guide to Choose the High-quality One


Cars had electronic components for braking, moving, stopping, etc. They ensure energy flow and signals within these electronic components. Further, they protect your vehicle’s electronic components. All in all, they are crucial components akin to the human body’s blood vessels and nerves. To perform these functions well, you need reliable wiring harnesses. This blog will read how the vehicle wiring harness works and how you can pick the correct one for your vehicle.

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What Is the Vehicle Wiring Harness?

Vehicle wiring harnesses, car wiring harnesses, or automotive wiring harnesses are not just covered tubes of some insulating material but also include cables and wires that connect various electrical and electronic components of the car. It allows wires to run through it in an organized fashion.

The wiring harness guides wires in and out of all electrical components of the vehicle, such as ECU (Engine Control Unit) relays, fuse boxes, lights, and other essential sensors such as TPS (Throttle Position Sensor), MAP (Manifold Absolute Pressure) sensor, fuel injectors, ignition coil, and ground.

It also consists of safety enclosures that prevent short-circuit fires and clean wiring.

Determining wiring harness quality

Most of the wiring harnesses look similar and are a bunch of wires and connectors. So, how will you pick a good-quality harness?

See the connection of connectors.

There are two ways to connect wires and connectors: crimping and crimping & soldering.

If there is only a crimping connection, it may not include all wire strands. If a crimped link does not have all the strands, it will conduct less electricity than a fully crimped connection. Less conductivity leads to more resistance, and that means less voltage. In a vehicle, specific components do not work at low voltage, or if they work, they may wear out prematurely.

On the other hand, crimping and soldering connections offer two advantages:

  • Firstly, there is no conductivity issue, even if it does not include all the strands.
  • Secondly, this combination is more durable than only a crimping connection.

In general, vehicles use crimped and soldered connections as the standard for racing and driven-off cars.

See if the harness is expandable.

It would help if you always looked for an expandable wiring harness due to following reasons:

  • First, an expandable harness can accommodate more amperage than the circuits it includes.
  • Second, for a more amperage harness, use heavy-gauge wiring.
  • Lastly, oversize wiring ensures the slightest voltage drop across each circuit. Further, it also provides that the harness work as expected in all conditions.

Image: a bunch of wiring harnesses

Ask technical support a difficult wiring question

Vehicle wiring is not simple. It would help if you had good tech support to install wiring, especially when you need a custom build. Ask specific questions from technical support. These may include:

  • How many circuits do you need in a year? 
  • Whether the harness is expandable?
  • What is the limit of the circuit?
  • Whether the connectors are of aluminum, copper, and brass?
  • Whether the harness is compatible with a 100amp alternator?

Choose proper wire

The market is flooded with several types of electrical wires. Choosing the correct wire for your application may be confusing, and choosing the wrong wire may lead to fires and failures. Before selecting the right wire for your vehicle, keep in mind these things:

  • Firstly, never use household wires in vehicles as they cannot handle heat, vibration, and chemical exposure.
  • Secondly, don’t go for cheap wires as they are primarily aluminum, and aluminum has less conductivity, so you will have to use high gauge wire.
  • Thirdly, don’t buy wires from discounted sites.
coils of electrical wires for installation in cars

Image: coils of electrical cables for installation in cars

Following is the list of wires that are most commonly used in different parts of the vehicles:

Primary wire or GPT:

  • It is a general-purpose automotive wire.
  • It is resistant to oils, acids, and harmful chemicals.
  • has a multi-strand core, and its flexible insulation allows easy pulling and stretching around tight spaces.
  • It can withstand a temperature range of 80-degree Celsius to 105 degrees Celsius.

Hook-up wire or Motor wire:

  • It has fine strands which can handle high voltages.
  • It is resistant to acids, water, fungus, solvents, and oils.
  • In addition to the automotive applications, you can also use them in the internal wiring of appliances.

SXL wire

  • These wires have a cross-linked PE (polyethylene jacket). As a result, these can bear high heat and abrasion and are more durable.
  • These wires are best for racing and industrial-use vehicles.
  • Like SXL, GXL and TXL wires have similar insulation but thin walls. These thin walls make it easier to pull them.

Speaker wire

  • As the name implies, you can use them for audio applications to carry sound from stereo to speakers.
  • These wires have paired stranded wires.
  • These are low voltage wires and thus cannot bear a high load.
  • Use their “+” and “-“ terminals correctly for improved sound quality.

Battery Cable

  • You can use these cables to connect the battery to the car’s system.
  • These cables have heavy and large gauge wire.
  • These cables are susceptible to corrosion.

Trailer wire:

  • A GPT wire, when colored and used for trailer applications, becomes a trailer wire.
  • Trailer wires have a coloring system that includes green, yellow, brown, and white. All these colors represent special lighting functions.


The advanced safety & infotainment features need high-quality wiring harnesses in your vehicle. If you are also looking for reliable wiring harnesses for your cars and commercial vehicles, we can help you. Gloom deals in superior cable assemblies and wiring harnesses, and we also offer you customized solutions.