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Wiring your Mopar
Stuff to know
Wiring is a common service we provide here at Muscle Rod Shop, be it on cars brought in for technical services that we did not build ourselves or cars going through the compete build process. This clipboard's purpose is to describe the options available to you as a customer or as a do-it-yourselfer.

The wiring in your muscle car is old. 50 year old! But that does not necessarily mean its bad. Wiring harnesses we see from the muscle car era didn't usually die of old age... if they are bad, its moreso because they were destroyed by 50 years of "fixes", "add-ons" and "upgrades". It is not always necessary to completely replace your harness. Portions that reside under the dash, or the sections that run to your headlights or tail lights might still be just fine. The engine section is usually beyond repair though, due to years of heat and oil.

Here at Musle Rod Shop, the decision to replace a harness depends on a couple of factors. Restorations or Resto-mods might or might not get new harnesses depending on current condition, the wishes of the customer, or the need for originality. Our Muscle Rods are highly modified cars with many upgraded, modern features that simply require a new, modern harness.

To break it down, there are four choices:


1. The original harness or one sourced from the same year make and model. Be aware there are subtle differences between the years, and even small differences depending on options and dash style.

2. An aftermarket harness designed to perfectly replace the original harness. These typically will have exactly the same wire colors, lengths and connectors.

  1. An aftermarket harness designed to approximate the original with most or all of the same connectors, but with a modern fuse box and accomodations for additional aftermarket components

4. An aftermarket harness not intended to replicate the original in any way, designed for a full-custom installation.

Here's more detailed breakdown:

1. Your original harness is useable if there are no cracked, broken, melted or cut wires and if all the connectors are present. Pay special attention to the firewall bulkhead connector to make sure there are no melted wires! As mentioned, usually the underdash harness is fine if the car was cared for and not modified over the years. You may only have to replace a section such as the engine harness, and even those are plug-in, requiring no splicing. Remember it is possible to extract single wires from your original harness for targeted replacement if necessary.

2. Original style restoration harnesses are purchased from suppliers such as Classic Industries, Year One, etc and are purchased by the section. The most common sections are Underdash, Rear Body (taillights), Front Body (headlights), and Engine. There are numerous small add-on sections available for other fatory options and features. These harnesses will have correct wire colors, connectors and lengths. Plug and play! The wire colors will be bright and new and the wraps will be original in appearance. Very nice! A quality restoration with original appearance, original components, and a reasonable budget will use this harness.

3. A full aftermarket harness such as American Autowire's Classic Update Series which is designed specifically for your car's year, make and model is the right choice when you need or want to replace the entire wiring system with a system that is close to but does not need to be exactly like the original. American Autowire goes to great lengths to supply a system with the correct connectors so that your original switches and components will plug in, but wire colors are not original to the Mopar schematic. Also, many of the connectors will need to be installed on the wires by the installer. There are many beneifts to this system if your car is not completely stock! Modern powerplants, gauges, fuel systems, electric fans, big alternators and other add-ons are great reasons to not go stock on the harness. Custom routing of the wires is so much easier, and the switch to the small mini-fuses is great. Additional circuits that were not needed by your stock car but are now are supplied. Use this system if your car is modified and you simply want an all-new system, but not necessarily stock in color and appearance. This is a sample of the full Update Series haress for your car:

4. The final option is a system such as American Autowire's Builder or Highway series harnesses. These are generic in design and there are levels of connectivity to choose from. These harnesses make no attempt to match your original system in wire color or connector supply, these are full-custom setups. Use this harness system if your are building a full custom car with virtually no stock components. You'll still get a modern fuse box with plenty of wire, plenty of connections, essential connectors and great instructions, but you also have the freedom of running your harness any way you like. We've zeroed in on the Builder 19 series for our Muscle Rod Shop full custom cars. In these cars, virtually all original components are upgraded, meaning that the original connectors are no longer needed. With a few simple hand tools, any connector can be connected to any wire with professional crimps and no splicing. For high-end customs, this is the way to go. Here's a sample:

So you see, its not about what style of harness is cool... its about what's best for your car depending on your level of originality or customization. Call us if you have questions about this subject and ask for Steve.
Doing your own wiring? Good for you! You will need the right tools to do the job right. A wire stripper is essential, and you MUST have the proper crimp tools. Aftermarket update kits will come with terminal ends that must be crimped on for a proper and professional installation. You will find that having the tools and thus the capability to properly crimp your own terminal ends will make a huge difference in the quality of the job. It allows you to add and remove terminals from all of those connectors and the bulkhead, meaning you can do a complete, professional and reliable installation with no splicing and little or no soldering required. (Note: we NEVER use those terminal ends seen so often on cars with the squished plastic sleeve around them... Unprofessional!) Especially when the proper tools and parts are readily available with a small investment in the right stuff. Needle nose pliers will help extract the male ends from most connectors and a very small flat-bladed screwdriver will help extract the female ends. Make your change, snap in a new end and you're on you way. With a little practice, you'll soon be finding that installing your own high-quality, professional harness is easy and fun, with a little help from American Autowire. And a little help from us if you need it.