American Autowire 1964-’66 Mustang Classic Update Wiring Kit

This is a review that I am looking forward to writing as I enjoyed the project, if I’m not careful this will go on for pages and pages! So where do I start?


If you follow my link to the “Original Wiring” (click here) under Photos section you will see why. The car was in a monster mess with bits of wire cut everywhere,  the bulk of it in what was left of a box, stuffed down the side of the rear quarter panel. So I needed a replacement wire loom, end of story! So I started research and discovered that there are various ways of doing it;

1) Getting an NOS (New Old Stock) wire loom, not much hope there, plus the wiring will still be old.

2) Get a custom set of wires made to fix what I have – expensive and I’m not gonna pay that!

3) Get a modern rewire kit.

Now the enthusiasts out there will have a mental and say “it’s not original, you have ruined it”. I have been told this already but my answer is short and sweet; “I want a safe car with electrics I can rely on, you can’t see the wires if I insulate them anyway!”

Decisions – Decisions!

So my options were quite straight forward in the end, a “Painless Wire Harness” kit or an “American Autowire Classic Update” kit which is what I obviously bought.

Tip 1) look into the import charges and customs costs. My kit cost me just under £400, and then another £135 with import costs and our wonderful HM Customs charges. I wasn’t expecting the additional charge but, it was still worth it. The painless Kit by comparison would have cost more and so more import charges. I won’t bore you all with the charges, but please do look into it if you are importing from the USA to the UK.

Decision made – American Autowire 1964-’66 Mustang Classic Update Wiring Kit it was.

What’s in the Box?

The box was heavy, in fact I was surprised at just how heavy it was. Thinking about it what did I expect? This is a wire loom for an entire car, and lets face it there more than just a few wires in there! Everything was there, a large rolled up bundle of wires and lots of plastic bags with parts in, such as a new ignition switch, new dimmer switch, fuses, relays, additional upgrade bits of wire, rear light connections and so on. There are the instructions which are double-sided A3 and numbered accordingly. There are packs of terminals and the plastic connections to make quick disconnects as you want, like i did for the dash guages. The bit I liked – the fact they gave you practice terminals to use instead of your own allocation of terminals. Nice touch guys.


Firstly I am NOT going to tell you how this is to be wired, what steps to take etc etc. as there are many more people out there who are more capable than I am at explaining things, in fact there are picture walk-throughs on some of the mustang web sites. I will however touch on certain points. The bits that I had issues with and the little extras that you need.

Ok, first of all there is a massive sign in the box that says STOP. This is relevant as the update kit does not support the Ammeter gauge in the dashboard, as a result I now have a dead gauge, I am thinking of replacing it with a clock, but I am not sure yet.

Update: March 2015

I used the space for a replacement voltmeter conversion, this was a fairly complex modification, but i talk you through it here: or click here for the link.

Basically this is a very sensible move as the gauge often burnt out and the connections are a direct feed from the alternator to the dash! Not an ideal scenario to be fair, so it was deemed safer to remove these connections. It’s a shame but there you go. Also the recommendation is to use a One Wire Alternator. In the UK these type of alternators are not that common, so I had to order one in so I could make the kit work as it was designed to work. It just meant that I had to get a chrome one as well, oh well never mind then! 😉

Anyway, this kit is NOT for Concours wire loom replacements. It’s as it says, an Upgrade Kit. Now the fact there is a requirement for a one wire alternator as an ideal shows the company are moving with the times to support modern technology. That meant that I could do away with the external voltage regulator and use one inside the alternator itself. I also upped the ante on the alternator to 100amps as well, that was in order to run everything I needed and the little extras I want to put in the car later on. The less connections and external parts doing things means less to go wrong, and make for a more reliable set up. I am not sure how many people who look under my bonnet will say that wire is wrong, only to go on and ignore the big fat chrome air filter I have sitting on top of the non standard Holley 600cfm, four barrel, carburettor under there? The upgrade kit does not fit with factory Air Conditioning which I have (had). The thought process here was simple, the radiator and condenser were not present under the bonnet. I have the original blower unit and the pipe work under the dash, which I will put back in later without the Aircon pipes. If I want the AirCon back I will make a custom route of pipes and fit them in. The reason you can’t use the factory AirCon is the fuse box fits right over the holes for the factory fitted pipes to the cooling blower under the dash There is no reason why you can’t relocate the fuse box if you are brave enough. Not ideal but I’m not after the AirCon just yet. I have the pulley in place, the alternative power steering pump and the mounting brackets, so if I do need to AirCon sometime It won’t be a major hassle!

The kit is basically a lot of wires that run from a new blade style fuse box instead of the old very sparse round glass fuses. The wiring loom is carefully thought out and each section of the loom is like a tree that branches of where it needs to go, such as the lights, dash, steering, rear end, fogs, heater etc. Each wire is colour coded and has written on each wire every few inches exactly what it is. Some of the wires are in a loop so there can be more than one wire called the same thing in each branch. The instructions are written out step by step, such as “1. attach connector type x on wire Ignition etc”. The instructions are clear and there is no techno babble in there that you don’t need. Careful explanations are given to the ignition circuit with the various options of wiring the car up. I had to take this into consideration when I was also in the process of installing my Pertronix Flame Thrower II kit. Click Here for that review. You can if you really want to use a standard alternator, but some additional modifications to the loom will be required to use the ballast resistor, solenoid and voltage regulator etc.

Tip 2) I photocopied the originals and laminated them. Simple reason is that I started to put dirty oily fingers over the originals. This laminating also helped with weight and the spots of rain that always seemed to appear when I was in the most awkward of positions! At least you can wipe the oil off the laminate and the rain won’t ruin the paper.

Where anything is more complex there are diagrams colour coded to show you what colour wire goes where and what it’s called. The whole set of instructions are in colour and makes things a lot easier to see at a glance. The reason here is that each wire is given its own colour code and its name printed on it so there is no mistake. The instructions also has a line up template where to mount the fuse box under the dash. Two screws hold the fuse box in place at opposite corners. I found the screws a little long, but soon covered them over so they can’t really be seen from inside the engine bay.

The first picture shows one of the instruction sheets to line up the mounting position. On the fuse box picture, you can see the oval under the screw which would be where the factory Aircon pipes would be coming into the car.

The replacement parts for the ignition switch, wiper connections, lights (and dimmer) are exact replacements for the originals, so they are just a direct replacement. Each branch has a given set of wire length to go where they are needed. These lengths are very generous to allow custom routing around the car and engine bay. The only real exception to this is the loom that goes to the back of the car, this has to run down the left side of the car. The rear light connections are “correct” replicas of the originals so you wont be able to see the new labeled wires there anyway once they have been wrapped up and covered in a flexi shroud to make it all look nice. The rear half of the car is a separate section and just plugs into the loom on the left hand side when you need it via a quick disconnect plug and socket fittings. Rubber grommets are supplied to pass the wires through the wholes in the fire wall where needed. These are essential as you don’t want vibration to cut into the wire casing and short the cables out. I also wrapped the cable heavily here as well, to look nice and also protect the wires.

The wiring for the ignition gives you options for the connections you have, old style ballast resistor or not, and the one wire alternator configuration. The removal of some of the wires has tidied up the engine bay around the solenoid area no end. There are additional courtesy lights supplied to replace under the dash. They are unfortunately plastic, I would have preferred metal to be honest, but you don’t see them and they will do the job fine. The light emitted from them is very good and better than the originals.


Any Issues?

I did come across an issue that was not the fault of the AAW kit. I followed the instructions for the gauges on my GT 5 gauge dash. Unfortunately the wiring diagrams for the dash was for a later ’67 models and did not cover my five gauge set up. The fact that all my GT dash wiring was vandalised (for the want of a better word) caused me massive issues. The AAW kit I was expecting to plug straight into the loom for the dash, but, as I had to make my own wire loom up I needed to know what went where. I contacted the after sales service who called me here in the UK to discuss the issue and what I needed. They provided me with a technical paper on what was required, connections as well as diagrams to support the work. As a result I am told there were changes to the instructions set to include the GT dash now. I can’t fault their expertise and helpfulness when I needed it, excellent after sales customer services.  The wiper motor is an issue for me at the moment. Due to the damage of the motor wires and the missing sub loom wires for it, the kit is not connected up yet for the wipers. I will replace the 2 speed wiper motor and get a replacement sub loom to make it all work.

Update: February 2015

I fitted a Newport 2 Speed Wiper motor in the car. I have reviewed the product and done a walkthrough fitting, click here for the quick link.

Tip 3) Get the right tools for the Job! This sounds daft, but there is a good reason for it. There are connections supplied that are the open style connections like those used on the original vehicles. The wire is placed in the open end, the first crimp holds the wire and the second holds the cables. This is different to the generic squash the wire inside the insulator (red, blue & yellow common types) and that will do. These connections require care and once you have mastered the technique they look brilliant.

The tools I will review at a later date on their own. They are available to hire only in the USA which is a shame, or you can buy them. They are  fairly expensive at just under $100 each.

You will need the p/n 500649 which will deal with the 20 – 14 gauge wires.

The p/n 500523 does the 10 – 18 gauge wires and double wire crimps.

I did try the practice terminals on some old wire and various types of crimps I tried. To be honest they looked inconsistent and took about four times as long. I wasn’t even sure I could trust the crimps to be honest after the crimp had been done. There are other multi tools out there that change the jaws to do the job. Now I don’t want to change jaws to do a single crimp and then change back again for another. These tools you pick up use and put down again. I would seriously recommend these tools for consistency, professional look, sanity and just plain ease of use.

I have reviewed these Crimping tools now (20/12/12) and they can be found here, or click on the Tool Reviews button on the home page.

You will also need a decent pair of wire strippers, click Here for my Toolzone review, a cordless drill and drill bit, electrical insulation tape, heat shrink wrapping (optional, but it does make the connections look that much better), split braid wire wrapping and plenty of patience.

Tip 4) Read the instructions carefully first.

Additional Information:

I have talked about the wires and getting the car to work, but this kit offers more: There are the connections for relays which tuck behind the wiper motor out-of-the-way.

There are connections for power windows, fog lights, electric fuel pumps, spare 12v feeds, quick disconnects for dash and steering column, the list just goes on!

You may not need all these connections but they are there just in case you do.

The links:

The main links section of the site will take you directly to the Kit I have, obviously you can browse from there but if you want the home page it’s here:

I have attached a link here for the tutorial on how to do the crimping from the AAW guys:

The quick sales pitch for the AAW kit:


I never thought I would be able to do it all on my own, I thought the plan would be to get most of it in and then get some help. In fact I needed none. I have left some of the wires a lot longer than I need as I will need to finish them of properly once I am satisfied all is in place and working as it should. Such as the Neutral safety switch and back up lights etc. These have been connected via a quick release, just in case I need to swap them around I can just pull the connectors out and rearrange them. Do that on the other wire kits if you can! If you have an old wire loom and it’s a little flakey and been butchered and spliced and looking to replace it. This is the way to go. If you want concours exact replacement this is not the way to go. For me this is what I needed. Replace the lot as new and enjoy the car, nobody will really know to be honest. The only time they might guess is when it starts and don’t break down due to wiring all the time!

Rating:  9 out 10

Update: 19/1/2014

The car was originally going to be sprayed with the loom in place, but I have been advised against that approach and to do it properly. As a result the loom has had to come out in order to do the paint properly. These pics here are of the loom on its way out.

Update: February 2015

Here is the car back from paint and the wiring loom going back into the car again. From the original storage of wires after the removal in a large waterproof box, all the way back to routing of cables and fitting.

So, the wiring loom was fitted once, removed, stored and fitted again after the repaint job. The loom stood up to the trauma without any problems, all the wires worked again. I redone some of the work differently this time to make the loom fit better. The only thing I can see that was an issue second time around was the horn wire wasn’t quite long enough for both horns. I fixed this by replacing a complete length to the second horde from the double crimp on the first horn.


The crimping of the connections on the wires has taken some fair punishment, much more than you would expect. Two fittings and a removal is more than most wiring looms ever get. Use the correct tools for the job and it will save you some serious headaches later down the line.


Another great fitting loom second time around, some of the wire markings got rubbed of on the heavy wear points, but as the wires are marked all the way along this wasn’t a problem to locate the correct wires again.

I’m delighted with this kit.

If you need to replace your wiring then this is the way to go, unless you want concours correct. But as i wrapped my loom in fabric OEM tape, you cant see the wires anyway.

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16 thoughts on “American Autowire 1964-’66 Mustang Classic Update Wiring Kit

  1. Sadly, I find myself in the same bind with my Fiat, the wire is just a mess and incredible difficult to work around

    1. Thanks for the comment its very frustrating to say the least, the car is never going anywhere until the wires are sorted out. So time consuming and nobody will ever know the hours it has taken to do.

      1. As of recently, the wires going to my ignition cylinder were damage and the car won’t crank and it incredibly frustrating like you said, because no one ever get to see this work being done and how much effort it put into it

  2. Have you ever thoughyt about creating an e-book or guest authoring on other blogs?
    I have a blog based on the same subjects you discuss and would really like to have youu shhare some stories/information. I know my visitors
    would enjoy your work. If you’re even remotely interested,
    feel free to send me an e-mail.

      1. Thank you it’s just something fun to do about food and whatever is in my head::) Good luck on your mustang .Live to ride:)

    1. Thank you for the kind words. I had a difficult choice like you for Painless or Autowire kits. I would genuinely love to know how you got on with the Painless setup if you could. I was after new fuses and options for extras if I wanted them. All the best with your project. My only tip is get the right tools for the job, wire strippers and crimps etc. It makes life so much easier.

  3. Hi, I did this in stages and took my time over it all. I would say that it took me around 4 or 5 days in total hours. I’m not an auto electrician so I had to learn the hard way – as I went along on my own. I dare it could be done faster with somebody who knows what they are doing. I have still to do the horn section as the wheel was not correct and the button itself was missing, but the wires are there ready though.
    Thanks for the question, if you have anything else you need to know I will try and help out where I can.

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