Understanding vehicle wiring

Wires allow electricity to travel from one location to another. Many vital systems in a vehicle won’t work if the wiring isn’t in place. Copper and aluminum are the most popular types of automotive wire materials. The difference between the two is that copper is more conductive, flexible, and unlikely to corrode than aluminum wire.

Wires come in a variety of shapes and sizes and can be found all throughout a vehicle. Some wires merely supply power or ground to specific components, while others carry a range of digital and analog signals to components such as the powertrain control module (PCM). The wire’s qualities are mostly determined by its intended function.

Car wiring harnesses

The different types of wires in a car, their functions, and their importance to the portions of the circuit that they connect to each other will be discussed in this article. We’ll also go through the signs and symptoms of bad wiring, as well as the sources of wire damage.

Read more: Understanding vehicle electrical system

What are the properties of vehicle wires?

The length, composition, size, and way a wire is wrapped can all vary depending on its use. Because a wire harness can only conduct a limited amount of electrical current, these qualities are crucial. If a wire receives too much current, it may overheat and melt. The following are factors that can determine the properties of vehicle wires:


The length of a wire has a direct relationship with its overall electrical resistance. As a result, a longer wire will encounter greater resistance, resulting in more energy being lost.


A wire is usually coiled to keep it organized. The way a wire is packed, however, has an impact on its ability to dissipate heat. When a wire is bundled with a lot of other wires, it can only carry a fraction of the current it could carry if it were the only wire in the bundle.


The most frequent materials used in vehicle wiring are copper and aluminum. Copper is less corrosive, more conductive, and flexible than aluminum. However, copper is heavier and more expensive. Aluminum, on the other hand, is less expensive and lighter, but it is less durable and more likely to corrode or develop electrical resistance over time. Copper wire is, however, employed in the majority of automobile applications.


A wire’s resistance is also determined by its gauge or size. The larger the wire, the lower the resistance it produces. The gauge of a wire determines its size. The smaller the gauge, the larger the wire. A 16-gauge wire, for example, is larger than a 24-gauge wire. Larger wires will be able to conduct electricity with less resistance since they have more conductive material. This is due to the fact that the amount of electrical resistance in a wire is related to its cross-sectional area in an indirect manner.

Read more: Understanding capacitor

What are the vehicle wire colors and what do they mean?

Wires harness for cars come in a variety of colors. Depending on its function, a wire is usually allocated a color. This facilitates repairs by allowing the technician to distinguish the function of an individual wire from a group of wires in a wiring harness.

However, many people believe that all wire colors are consistent and that each color corresponds to a specific function. In reality, the purpose of a wire color varies based on the year, make, and model of the car. You must read your car’s electrical diagram in its service manual if you want to learn about the function of each wire color of your vehicle. Manufacturers publish service manuals, which are duplicated in repair manuals and repair databases.

What are the types of wires used in vehicles?

Wires come in a variety of shapes and sizes, and they’re employed in a variety of applications in a vehicle. It can be difficult to figure out what kind of wire you need. However, making the appropriate choice is crucial because employing the wrong wire type can lead to failures and fires. The followings are the common types of wires used in vehicles:

  • GPT or Primary Wire
  • Motor Wire
  • TXL, GXL, SXL Wire
  • Battery Cable
  • Speaker Wire
  • Trailer wire

Read more: Understanding alternator

GPT or Primary Wire

In auto shops, this is the most common wire. The most prevalent form of automobile wire is GPT, which stands for General Purpose Thermoplastic. It contains a multistrand core and flexible insulation, allowing it to fit into small areas. GPT wires, unlike other wire kinds, aren’t meant to be exposed to the outdoors for long periods of time. GPT wires are generally utilized for interior applications because of this.

GPT wires can withstand temperatures of up to 176 degrees Fahrenheit, however, some are rated for temperatures as high as 221 degrees Fahrenheit. Oil, chemicals, and acids are not a problem for these wires.

Motor Wire

The major difference between GPT and motor wire is that the motor wire’s insulation has finer strands of copper wire. It can withstand greater voltages without burning up as a result of this. Motor cables can endure 600 volts and temperatures of up to 221 degrees Fahrenheit.


TXL wires are stranded, single-conductor copper wires that are insulated with cross-linked polyethylene. SXL wire has a bare copper conductor and is insulated with cross-linked polyethylene (XLPE). GXL wire, on the other hand, is a single-conductor primary wire with a thin wall and XLPE insulation.

The cross-linked polyethylene jacket on the three wires is more heat, abrasion, and age resistant than the GPT wire. In high-stress applications such as racing or industrial vehicles, SXL wire is typically the preferred choice. If you require extra durability, this is a fantastic option.

TXL wires are similar to GXL and SXL wires, except they have thinner insulation. The insulation thickness of a wire can differ based on where it will be put. Wires that are thicker are more durable. Using the thin TXL wiring, on the other hand, is ideal for racing automobiles because it may save a vehicle up to six pounds of weight. GXL wires are a cross between SXL and TXL wires in terms of thickness.

Battery Cable

A battery cable connects the battery to the vehicle’s electrical system (usually the starter) as well as the ground. It’s a thicker, smaller-gauge wire.

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Speaker Wire

The audio signal is sent from the head unit or stereo receiver to the speakers through speaker wires. Speaker wires are designed for low-voltage applications. The positive and negative terminals of the wire must be installed in the correct locations. The speakers will not sound right if this is not done.

Trailer wire

GPT or main wire that has been colored and tailored for trailer use is typically used as trailer wire. The majority of trailers have a color scheme that incorporates green, yellow, brown, and white.

Read more: Understanding battery used in automobiles

What are the signs your car has damaged wiring?

Wires provide a conduit for electricity to pass between the various sections of a circuit, as previously stated. When wires fail, the vehicle usually exhibits symptoms that correspond to the connected component. The following are the most common signs that your vehicle’s electrical system is beginning to fail:

  • Vehicle electrical components malfunctioning
  • Fuses keep blowing out
  • Car starting issues


Vehicle electrical components malfunctioning

The most prevalent indicator of damaged wiring is electrical components that don’t perform as intended or don’t work at all. Wiring faults can result in a number of electrical issues, ranging from a broken radio to a car that won’t start.

Fuses keep blowing out

When there is too much electricity running through a circuit, a fuse is designed to blow. A shorted wire can cause an excessive amount of electricity to flow through a circuit, resulting in a blown fuse.

Car starting issues

If your engine won’t start, it could be due to a wiring issue, such as a corroded PCM ground wire or a damaged wire in the starting circuit.

Read more: Understanding the types of automotive fuses

What are the most common signs of wire damage?

Short circuits, open circuits, and high resistance are the three most common types of damage to automotive wiring.

Short circuit

Wiring to power or ground can become short. The components within the circuit may perform erratically or not at all, depending on how and where the wiring is shorted.

Open circuit

When the wiring is cut, current cannot travel from one end of the circuit to the other, resulting in an open circuit.

High resistance

High resistance can obstruct current flow, causing the circuit’s electrical components to perform badly or not at all. High resistance can be caused by issues such as rusted or improperly connected wiring.

Read more: Understanding ultracapacitors

In summary

A vehicle Wiring harness is the complete wire structure or framework system that supplies power to a vehicle’s electrical system. These wires are of different types and vary in properties because they give power components that require different amounts of electrical power.  In this article, the properties, types, and common signs of damaged wires are discussed.

I hope you learn a lot from the reading, if so, kindly share with others. Thanks for reading, see you around!