BY Ron Ceridono Photography by Jason Scudellari

or most of us the prospect of wiring a car ranks right up there with going to the dentist for a root canal—in both cases a certain amount of worry results from anticipating the uncomfortable procedure about to take place. While we can’t do much about visiting the dentist, we can advise the easy way to wire your pride and joy, and that’s with a wiring system from American Autowire. To install it you don’t have to know any more about electricity than that it’s the stuff that makes the engine run when you turn the key and the lights come on when you pull on the switch.

There are a variety of reasons for rewiring an older car, and in many cases time has taken its toll on the original electrical system to the point that safety and reliability become issues. Over the years, wires and connections will deteriorate, and it’s not unusual for ill-advised and poorly executed modifications to have been made. But more often than not updates are needed to add electrical accessories that the vehicle was never equipped with. To address all those issues, American Autowire offers three types of wiring solutions:

Factory-Fit OEM Reproduction Wiring Harnesses

These harnesses are made for GM vehicles using original engineering blueprints. They are plug-and-play replacements and each section (underdash, rear body, and so on) is available as an individual part number. You can replace all the wiring or just sections as needed.

For those updating to a more modern, high-energy ignition system, or installing an internally regulated alternator, American Autowire can also modify many engine and front harnesses for these upgrades.

Classic Update Kit

Classic Update kits are designed for restomod applications. They are available for over 60 makes and models and completely replace the original wiring harness. Included in the kits are the correct, original-style lamp sockets and connectors. A modern, ATO-style fuse box and additional circuits for options such as A/C, power windows, fuel injection, and more are included. Each kit is engineered for a specific year/make/model combination and can handle most stock and aftermarket components.

Universal Wiring Kits

American Autowire’s universal wiring kits are for custom applications or a situation where there is not a Classic Update Kit available for your vehicle. The Highway Series kits allow the installer to choose where to locate the fuse block and how to route the harness to suit the car. The PowerPlus, Builder, and Route 9 kits are designed to have the panel mounted under the dash. American Autowire suggests large-capacity panels, such as the Highway 22 Plus, PowerPlus 20, and Builder 19 for electrically intensive cars. For applications with fewer electrical demands the Highway 15 Plus, PowerPlus 13, or Route 9 kits provide for necessary items with a little extra room for added accessories in the future.

One of American Autowire’s most popular kits in the Highway 22 Plus Universal system is the one we chose to install in a ’70 Chevy Nova. The fuse panel comes with an LED flasher, horn relay, and a pre-installed relay for accessory circuits that can be triggered by 12 V or a ground circuit. Wires in the kit use GM’s color code and are labeled every 3 to 4 inches.

To eliminate trips to the parts store, the kit also includes ignition, headlight, and dimmer switches along with a new high-amp alternator and main power connection kit. For our application we opted for the Highway 22 long wire kit that allows the fuse panel to be mounted in the trunk.

Installation Tips

American Autowire goes to great lengths to make their kits easy to install, but the best way to ensure success is to start by reading the full-color instructions. Once you’ve done that, familiarize yourself with all the components in the kit—everything is in bags identified by letters that correspond to the instructions.

With the Highway Series of universal kits, the fuse panel can be located almost anywhere it’s protected from the elements and readily accessible (OEM-style kits mount the fuse block in the original location). When routing wires keep them away from heat sources, such as the exhaust system, and anything that could snag the harness, like the driveline or engine cooling fan. If wires run through holes in the body or chassis, American Autowire recommends an insulator, such as a grommet, to prevent rubbing through the insulation and causing a short.

When it comes to potential problems with any electrical system, the one thing that causes more issues than anything else is a bad ground. For a circuit to work correctly there must be a good ground path leading back to the battery. So, while it may be heartbreaking to do, any painstakingly applied paint or powdercoating must be removed from any grounding surface.

Although American Autowire’s instructions are clear and concise to help avoid any problems during installation, they maintain a website full of FAQs and technical help is a phone call away. In the great scheme of things, installing an American Autowire wiring harness isn’t difficult—and it’s a lot less stressful than going to the dentist.

3. This Classic Update harness uses an integrated fuse block (the wires are already attached) that mounts in the factory location. Having the wires attached eliminates the difficulty of making connections under the dash.

5. For our installation, we used an add-on American Autowire trunk-mounted wiring kit (PN 500839). This kit is only for use with Highway 22 Plus harnesses.

7. The length of the wires in the Highway 22 Plus kit allows for custom routing—they are then cut to length as necessary.

9. Once the wires are cut to length, the supplied ends for the various applications are crimped on. Note the small tabs on the ends, they will lock metal ends into the corresponding plastic plugs.

11. Once the terminal is crimped on the wire it’s inserted into the plastic connector until it locks in place. This is a headlight harness plug; the second wire feeds the headlight on the other side of the car.

13. The Highway 22 Plus kit includes a dash-mounted ignition switch. As an option, a GM column-mounted ignition switch can be used.

14. When wires pass through holes in sheetmetal they must be protected. Rubber grommets work best and the plastic wire loom also adds protection.

16. Standard heat shrink tubing comes in a variety of sizes and usually has a 3 to 1 or 4 to 1 shrink ratio. There are a number of ways to heat shrink tubing; heat guns for stripping paint work very well and are less hassle than matches or lighters and probably safer, too.

19. For a battery, we chose an Optima AGM (absorbed glass mat) as the design eliminates liquid, making them spillproof. The hold down is from Eddie Motorsports. American Autowire offers premade battery cables with 1-gauge wire for top- or side-post terminals in lengths long enough for our trunk-mounted battery.

21. A master shut-off switch is handy during maintenance or repairs when the battery should be disconnected. They can also serve as a security device. American Autowire offers a variety of such switches with levers or removable keys.

23. In most cases the wire from the alternator will join with the positive battery cable at the starter solenoid. In some Ford and Mopar applications this connection will be made at the starter relay.

24. This harness is for the Holley EFI that the Nova is being equipped with. The Highway 22 Plus fuse panel will provide the electrical source needed for the EFI computer.