Wiring 101: The ABCs of Wire Repairs

There’s a first time for everything. There’s also the “second” first time, which usually stands out in your memory much more than the original. Like the first time you looked at the wiring harness in your project car. Sure, it looked a bit intricate, but nothing you were too concerned about. Then you discovered you needed to make some wire repairs or modifications, and you looked at it again. In a different light, it suddenly became an overwhelming and headache-inducing experience you’re not soon to forget.

Wire repairs are extremely common and will need to be performed regularly throughout the life of a vehicle. It doesn’t matter what it is or who’s driving, the wiring needs to be kept up with. So if we can’t avoid the irritating maintenance, we might as well learn some of the basics ourselves, right?

Safety First

In any situation where you are performing wire repairs or are adding in new wiring, disconnect the battery to ensure no power is in the system. This is a necessary step to ensure you don’t get shocked. It’s also done to prevent shorting out or potentially damaging circuits. If you’re running diagnostic tests you will want to keep the battery and wiring connected, so you can use a test light and multi-meter to test voltage. Otherwise, any time you’re planning to splice into or alter wiring, make sure the positive and negative terminals are disconnected.

Whenever you pick up a new project car, take some time to look over the existing wiring. This is a step you should take even if you don’t plan on changing the operating system in any way. Faulty wiring can be incredibly dangerous, so look over the entire harness from front to back looking for any chewed up or sketchy looking wires. “Put in simple terms, if it doesn’t look good, it probably isn’t. And even if it does look good, there are specific items that must be addressed during the installation process to ensure a quality job that won’t have you searching for issues in the pits, or worse, the staging lanes,” says Dragzine in its article titled, “Top Ten Wiring Tips with Ron Francis.”

Wire Gauge

When you find the problem, or simply the area where you want to add wiring, there are a few things to keep in mind before you cut into the system. First, make sure that the wiring you intend on using is up to spec because not every switch, signal, or circuit is going to run off the same sized wires. For example, due to amperage, headlights run on a thin wire gauge while the battery runs on a very thick wire gauge.

“The main issue for wiring is the sizing,” says NAPA in its “Know How Notes: Automotive Wiring Guide.” They guide says, “Wire is used to carry electrical current; how much current it can carry is directly related to the length and the thickness (or gauge) of the wire… As the distance from the source increases, the diameter must increase as well. [Additionally], any time you run wire, there will be a certain amount of voltage drop. Just like a water hose, the longer it is, the lower the pressure on the outlet. In electrical circuits, you can combat the voltage drop through larger gauge wires.”

For clarification, we’ve included a chart that provides a great breakdown on wire gauge requirements in relation to length and amperage. Wire repairs require a fair amount of homework. Understanding the basics of wire gauge will ensure you won’t run into issues anytime soon.

For clarification, we’ve included a chart that provides a great breakdown on wire gauge requirements in relation to length and amperage. Wire repairs require a fair amount of homework. Understanding the basics of wire gauge will ensure you won’t run into issues anytime soon.

Repair or Replace

Any sort of damaged or corroded wiring will need to be replaced. When fixing up an old harness you need to be considerate of how much time you are spending performing wire repairs. Sometimes it’s simply better to call in reinforcements and update everything. This might mean swapping out the entire harness from front to rear. But remember, the time and money that would go into repairing a heavily damaged one will greatly outweigh the smart investment of new parts.

Similarly, vehicles with custom drivetrains and updated electrical systems require plenty of quality time with wire repairs. And at a certain point, you might want to ditch everything and simply run a custom wiring harness. Painless Wiring is a leading manufacturer offering harnesses for both old and new custom builds. Remember, however, that these are chassis harnesses and in order to run a custom drivetrain, an engine wiring harness will be needed. So if you’re performing something like an LS, third gen Hemi, or a Coyote 5.0 swap, you’ll need a harness for engine management. This is due to the computers and sensors needed to run the engine.

Practice Makes Perfect

Harnesses, Tachometers, auxiliary lighting, sound systems, and all other sorts of electrically powered upgrades require tapping into the system with splicing and connections. Like water, electricity needs to flow. This is why making solid connections is so important. You want to make sure that you’re using connectors that are paired properly with the gauge of wire you are using; too big or small will prevent electricity from flowing from point to point. You also need to make sure you have the right tools for the job, as they will dictate how well the connections are made. (Stay tuned as we’ll be exploring that topic later this afternoon!)

In truth, it’s near impossible to discuss everything you need to know about wire repairs, especially when factoring in custom builds. But if you keep these basic tips in mind, do your research, and practice a little patience, we have faith that you’ll manage just fine. Remember that wire repairs can be tricky, and you’ll probably get lost the first (and maybe even second or third) time. Work smart and don’t be afraid to call in the professionals if you really muddy things up.

Find this post informative? We want to know what areas of wiring you want to learn more about—auxiliary lighting, stereos, ignition systems? Give us some feedback in comments section below.

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