Automotive Wire Harness Repair: What to Know Before Replacing the Entire Harness

The cable harness is like its nervous system, which helps carry current and signals from and to the different computers of the vehicles. Vehicle makers bundle these wires together for easy installation and management. These bundles or harnesses have a protective covering and are routed in the whole car, so they do not get damaged with use. In most vehicles, a factory wiring harness can last a lifetime without causing any issues. However, this is not the case every time. As a result, automotive wire harness repair is a core competence in the automotive industry.

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How does an automotive wire harness get damaged?

Due to the rough terrains and bumpy roads, the harnesses connected to the engine or the chassis undergo constant vibration, extreme stress, extreme temperatures, ice, salt, and flexing, which causes a significant impact on the wiring. 

Also, automobile wire harnesses have to face extreme weather conditions. Rainwater splashed through the tires to the engine and chassis, leading to the corroded wires and terminals. With corrosion, the copper strands become weak over time leading to wire breakage.

Automotive Wire Harness Repair: Dusty auto wiring harness

Dusty auto wiring harness

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Can an auto wire harness be repaired or overhauled?

That depends. How? Let’s know about the wire harnesses components first.

  • Connectors
  • Backshells
  • Wires
  • Splices
  • Terminals
  • Contacts
  • Shrink tubing
  • Braid or string tie

Every circuit comprises different components, so wire harnesses are of different types and their damages. Depending on their basic manufacturing and the damage, these are the following situations to know when you can go for electrical wiring repair.

  • You can replace or repair connectors if there is damage or corrosion.
  • If the problem lies with back shells, you can quickly get them replaced or repaired.
  • If the wires are damaged, you can go for cable repair.
  • If other components like splices, terminals, or contacts are damaged, get them repaired or replaced.
  • You can go for repair if one or two of the parts are damaged. Sometimes, the damage in even one piece is extensive, like melted wires. If more than 3 or 4 parts are showing problems, it is more economical to get the parts replaced rather than repairing them. 
  • If the wiring harness is injection molded, it is better to go for a new harness as repairing will be more expensive.
  • The wire harness’s size and exact location decide the installation cost. So, if the wire harness is difficult to locate, you are supposed to replace the whole one.
  • It is advisable to go for an entire wiring harness replacement for a sensitive part like an airbag wiring harness.
Automotive Wire Harness Repair: 
 automobile harness repair

automobile harness repair

Things to keep in Mind Before you go for an Automotive Wiring Harness Repair 

The complex and sensitive wire harnesses complicate this work. As you know, small cross sections of the cables, wires, and terminals, sensitive electric signals traveling at high speed, and much less space restricting access to the repair area and networked electronics increase the difficulty of repairing.

But, we still want to offer some advice on automotive wire harness repairs:

Safety first

Whether you are repairing or adding new wires, remove the battery to avoid damaging circuits from short circuits. However, if you are doing some diagnostic tests, you may need the battery for test light or multilayer tests. In that case, you can keep the battery connected.

In addition, when you start repairing work, you must first look at the overall wiring to notice any faulty wiring. If you see any wire as chewed up or sketchy, don’t touch it. The defective harness can be highly dangerous.

Know the circuit

Today’s vehicles have computer-controlled electrical circuits, which are challenging. While repairing, it is essential to understand the course. There are several low voltage signal-carrying methods in modern vehicles. If you accidentally solder them too much or splice them too long, you can add high resistance to the system, leading to signal error and computer miscalculation.

Match the wire gauge 

You must know the basics of wire gauge and choose a wire with specifications matching the corresponding signal, switch, or circuit. For example, the headlights run on a thin wire gauge while the battery runs on a thick wire gauge.

Always match the wire gauge with their function, too thin wires can result in a power surge, while too thick add more resistance to the electrical current path.

In addition, you must understand that the length and gauge of the wire decide its current carrying capacity. When the distance from the source increases, the diameter must also increase. Further, there will be a higher voltage drop with the increasing distance. So, to combat this voltage drop over long distances, you need to take thicker gauge wires.

Break wires out of the harness carefully.

If you are replacing or repairing a secure wire from the harness, you must remove that wire very carefully. The forceful pulling damages the saddle and connectors. Be careful while bending the cables and connectors. 

Avoid using solid core wire.

The vehicles undergo constant vibrations and shock, which may damage stiff solid core wires. Temporarily it can work for you, but it will create problems down the line. 

Ensure connectors and back shells are in good condition.

If you see any damage in connector heads and back shells, replace them before you install the wiring harness.

Pick the right connector size.

You must get the right size of connectors, especially crimp-style ones. If you pick too big connectors, you fail to make a solid crimp, and if they are too small, you may need to strip the wire stands to fit them into a minor crimp, which can weaken the circuit. Also, try to strip off enough insulation from the wire so that the crimp only touches the conductor, not the colored insulation.

Use heat shrink tubing to secure wires.

Once done, wrap the wires in the correct heat shrink tubing. Pick a heat shrink tubing slightly larger than the wire so it can easily slip over and fit the wire on heating.

The heat shrink tubing protects the wires from dirt, moisture, and various contaminants, which can cause risks to the electrical connection. The heat shrink tubing can provide a stable and stronghold, and heat shrink tubing with crimps is more effective and reliable. Use wire or automotive harness tape to create a waterproof seal.

There is heat shrink tubing which helps in connectivity and in bundling wires into a single harness. These tubes have premeasured solder added to them. Also, there is some tubing with adhesive lining. Such tubing can soften on heating and take the shape of the bundle offering more significant support and insulation.

On repairing multiple wires, use heat shrink tubing on individual repairs and then use a long tube to bundle all strands together for a clean look.

No quick connector kits

You must not use quick connector kits if you notice any cut wire on the harness. These simple connectors made of plastic, which can lock two or more wires together, should be strictly prohibited in this case. Although they are very convenient, they leave the wires open and do not offer a tight grip, leading to poor contact and intermittent faults. Even if you heat shrink them, it is not sure that their connection will last long.

No electrical tape

You all know about the black electrical tape, which is handy in most wiring. However, for new faulty repairs, you must not use this tape. The temperature variations and the moisture can loosen this tape over time. You can use electrical tape only to bundle the wires and not for their protection. 

No twist-on connectors

If you are using a twist-on connector after twisting wires, it is also not safe to go, especially on UTVs and ATVs. These twist-on connectors create a cup-like structure that accumulates mud or water, leading to their corrosion over time.

Butt connectors depend

It is a good idea only if you properly do it for corrosion protection. If you commit any mistake while using butt connectors, you may leave some open space leaving the wires exposed to water intrusion and humidity.

Best way to make a connection

The best way is to use a butt connector with a heat shrink tube. 

First, make the connection, crimp them and then secure them with heat shrink tubing to seal them properly. In this, you must use the right side of the butt connector. Be careful not to crimp the connector too hard that it damages the shrink tube laid around it.

For a more professional connection, use a part of heat shrink tubing. Now, put this tubing before starting the relationship and solder it. Keep the link hot enough to melt the solder to flow down into the wire and not just get wrapped outside it.

Let the tubing cool down before applying the heat shrink gun. On applying the heat gun, put the connection in the middle. Use the heat shrink tubing with gel filled inside to cover the relationship and encapsulate it properly when it shrinks with heat.

Automotive Wire Harness Repair: 
 complex wiring harness for the car building industry

complex wiring harness for the car building industry

Further troubleshooting auto wiring harness problems

If your auto wiring harness repair fails to make the system work, you are supposed to check some other components.

Automotive Wire Harness Repair: Clean the battery

The corrosion of the post can prevent a battery cable from functioning correctly. As a result, it can create problems in starting the machine. If you are not using your vehicle, it is a good idea to pull the positive and negative leads off for cleaning them. You can clean the battery posts with a wire brush. After cleaning, reconnect them. Spray a high-quality cleaner and protector.

Automotive Wire Harness Repair: Replace the fuse

If a fuse blows and you replace it with another with a more significant value, it will not work for a long time. However, if a fuse blows even if you use it in the correct amperage, it indicates some problem with the machine. The problem can be related to a short or overloaded circuit. Try to find it and fix it as soon as possible.

Automotive Wire Harness Repair: Check Add-ons

If you are adding a light bar or any sound system, pay special attention to the routing of wires. Always remember that if you’re going from one end of the machine to the other, follow the already existing harness as the manufacturer has used that path to keep the wiring safe from the heat. Look for the thing around the wiring. If there is exhaust or any suspension pivot points, it will affect the wire when it comes in contact with heat.

If you are adding new wires, don’t add them to the existing wiring harness, as it can carry only a specific load to the machine. Use a separate harness other than the main harness. Or it is good to use a relay. Using a harness to activate or deactivate something with a relay transfers the load from the saddle to the battery. As a result, there is no extra stress on the main harness.

Automotive Wire Harness Repair: 
 Wiring harness for engine control 

Wiring harness for engine control 


Thus, to ensure long-lasting wiring harnesses, it is good to take the right actions and use high-quality materials. Cloom can help you get the superior quality custom wiring harness you want. We are a leading automotive wiring harness manufacturer. Contact our professionals, who will guide you to the best possible deal. Our experienced auto wiring repair technicians will also offer convenient repair on products.

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Enjoy a free sample worth UP TO $100!
Explore our custom services now. Email us at [email protected] for more details.

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