Rats nest, spaghetti, copper conjunctivitis; call it what you want, but wiring is the single most feared aspect of all automotive projects. Whether you are chasing gremlins through a 50-year old survivor, or re-wiring your muscle car, most gearheads just don’t enjoy wiring. It doesn’t have to be this way, though, there are tricks and tips that can turn a nightmare into a job well done. And you don’t have to have a degree in electrical engineering either.
There are two main types of wiring projects: fixing an existing system, or replacing it. When you are dealing with 40+ year old wires, often the best solution is total replacement, especially if you have the car apart already. That is where we are going to start; a total rewire on a 1967 Corvette. This car came into the shop, as many do, fully disassembled; one man’s failed build sold off to another. While we had the original harness, most of the terminals were broken, the wires cracked and corroded. It simply was not worth trying to fix, especially considering the car was being fully rebuilt. Starting with a clean slate is always nice. We made a call to Painless Performance and they sent us the harness we needed.
We could have ordered a factory replacement harness, which is pre-terminated and bundled just like the factory harness; everything is where it should be for the stock components, but that would not work for our project because we had installed an LS1, electronic transmission, aftermarket gauges, and all the new-fangled goodies you would find on a new car. We needed to plan out new routing for this complicated wiring system. To do that, we ordered a 12-circuit universal harness, LS1 engine harness, and a really cool system called Phantom Key. The Phantom Key is a transponder-based push-to-start module that eliminates the need for a key. Just hit the button to unlock the doors, get in and hit the button to start, just like the newest cars coming out of Detroit. This provides the ultimate in regards to the cool factor.
To get started wiring, you need some tools. It is important that you use quality tools for this, because some cheap versions can cause more problems down the road. The most important tool you will use in a wiring job is the crimpers. Crimp connections often get a bad reputation because of poor installation. A properly made crimp is just as good as a solder joint. The key is correctly sized terminals and quality crimpers. Those cheap combo crimp-n-strip tools are not any good, throw them away. They are only good for emergency repairs. You need a set of good crimpers designed for insulated terminals. Klein and KD tools make excellent crimpers.
Wire size to terminal selection is critical. Using too large of a terminal will result in a weak connection. Most terminals are color coded for size. Red is the smallest, fitting 22-18 gauge wire, blue for 16-14 gauge and yellow for 12-10 gauge wires. Anything bigger is sold by the size, not color. Primary wire, is typically an 18 gauge wire, this is the most common wire you will find in a wiring harness. The larger wires that feed heavy-draw circuits are typically 14-12 gauge wire. The wire in our Painless kit runs a little larger than the standard; the primary wires are 16 gauge, with 12 gauge for heavy draw items such as the headlights.
Once you open the box, and see several thousand feet of wire, it can be scary. Fear not, it is not that bad, just be patient. The first step is to take it all out of the box and lay it out on the bench or floor. Separate all the bundles. The Painless kits come pre-bundled in all the major groups: engine, dash, and tail. From there, they are broken down into subcategories. These are good for the typical project, but you may find a few wires that need to be moved to a different section. Now is the time to reroute any wires. Once you are in the car, this becomes much more difficult. Go over each wire and its location and check the car. For example: if you are installing an electric fuel pump under the hood, then you need to alter that wire’s routing, because it would normally be found in the tail section.
All Painless wiring kits provide only the power side of the circuit, save for a couple of situations, you must provide all of the ground connections. While this is typically a simple thing, Corvettes require some additional forethought, because fiberglass does not a good ground make. Painless Performance thought ahead on this one. They offer a ground kit that comes with wire and several terminal strips to provide multiple ground circuits where you need them.
Wiring an entire car requires planning, time, and lots of patience. If you find yourself getting frustrated with a particular section, get up and walk away for a minute. Without juice, it isn’t going anywhere. A novice builder should be able to complete a basic wire harness replacement in 3-4 days. The more circuits you have and the more complications you add, such as EFI, audio systems, etc, the longer it will take. If you take your time and plan out the locations of all of the wires before you cut anything, your wiring project will look and function great.