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American Autowire Harness Install (2016)

This project started after a failed attempt to get the car running after puttin my engine back in. I ran into far too many wiring issues with the original 50 year old wiring harness and finally gave up and decided it was time to bite the bullet on this project. This harness has outlived what should be it's expected lifetime, but I was always hesitant to undertake rewiring the entire car. My previous wiring experience had been limited to minor wiring fixes, wiring in the after market gauges, etc. I looked at the various options available from universal harnesses to the factory replacement type kits from companies like Painless Performance and American Autowire. Based on the modified nature of my car, my wiring experience, and the numerous reviews I had read I landed on going with the American Autowire harness as a replacement. The kit I used is here at the American Autowire site. It is ideal if you have things like a 1-wire alternator, electric fan, etc.


I am not going to provide a complete guide to the kit as there are a number of good references including the following:

There are plenty of additional resources on this topic, but these were the main ones I used that I found.


For the installation you really need to buy the recommended crimping tools. The good news is the price has come down a bit if you buy the set for $150 at SummitRacing.com. I decided to buy the Painless Performance Classic Braid as well to wrap the entire harness in. Alot of guys are using various products depending on the cost. The Classic Braid is somewhat more expensive, but the quality of the product is great. If your budget can afford it I would highly recommend it. The one negative is the wrapping of this took considerable time overall. In the end it is well worth it and I expect that this harness being fully protected will last as long as I own the car. They recommend soldering every terminal that you install. Luckily I was able to borrow a high-end soldering kit to help with the installation, but you should be able to make due with whatever soldering kit you have available.


Like any project there are some specifics I did on my install that I will note:

  • Fuse box location - The kit wants you to install the fuse box on the firewall right where the factory AC hoses go out. My car has a factory AC and I wanted to retain it, so I chose to install the harness in basically the same location that the factory harness is located. I did not run into any issues with this other than I think it is probably slightly more cramped installing it here especially because I have the hardware for the Modern Driveline hydraulic clutch that shares some of that same space and isn't on many installs.
  • Neutral safety switch bypass - Since I have a T-5 and don't have a NSS mounted to my clutch pedal (or something similar), I decided to wire the kit up without use of a NSS. To do this they specify soldering the 6 (Purple - Starter Solenoid) wire to the 5 (Purple Neutral Safety Switch). Effectively all this is doing is extending the 5 wire to get to the starter solenoid. The alternative approach (as long as your routing location allows) is to just attach the 6 wire directly to the "S" terminal on the starter solenoid. This worked for me because I put the starter solenoid under the fender to get it out of the engine bay.
  • Hidden engine bay wiring - I have made multiple attempts to remove as much wiring from the engine bay as possible just to remove the clutter and give it a cleaner look. I ran the main wiring under the passenger side fender to the solenoid and the front of the car. AWW provides you with enough wire that you can run it pretty much however you want, but I found it easiest to route on the passenger side. I placed the MSD 6AL box and coil behind the glove box in the interior, and I ran the sensor wires (oil and temp) and distributor wires from the firewall through one of the holes where the heater hoses normally run through. Not sure how well this would all work if you had a heater and AC to contend with, but should be possible if you are down one or the other at a minimum. In routing the wiring through the passenger side I had enough wire for everything except the horn and the left turn signal. I had to extend those wires.
  • T-5 backup light wiring - Some people don't hook up their backup lights... I am not sure why... but I wanted to get mine hooked up so the car was more complete (and safe). The kit didn't explicitly explain how to do this but I found some information on it here. Effectively you need the T-5 backup harness (they are around $15) and you need to wire up the 24 (Light Green Backup Light Switch) and the 39B (Pink 12 V Ignition) wires to it. I routed this out through the engine bay, but you could run it through the floor or whatever location you choose.
  • Hurst Roll Control - If you have ever had one of these you will want one on every hot rod moving forward. I had one on my 06 GT and loved it! I had been looking for an excuse to add one to the 66 and a re-wire project seemed like the appropriate time. I wired in a light on my gauge cluster (red light between the speedo and tach) to let me know when it is engaged and used the switch that comes with the kit that mounts on the shifter. The AWW kit made this a snap as the connectors to the gauge cluster had provisions for a few additional items and I just plugged my extra wires in there and now my entire gauge cluster and additional wiring needs attach and detach with two quick connections.

Project Pictures

American Autowire Kit

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Painless Performance Classic Braid Harness Kit

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Damaged wire on old harness (Found this numerous places)

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Parking light with classic braid installed

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Bracket with MSD Box and Coil

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Another view of the bracket

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