It may be hard to believe but Fox body Mustangs are old cars. Consider that when Editor Creason (who is also the author of this piece) entered high school, first generation Mustangs had not yet hit the 30 year mark and even the Mustang II was less than 20 years old. Today, the youngest Fox body cars on the road are over 21 and if you rewind the clock 30 years you end up in 1984. Somewhere in between those numbers is our Project Rehab 2.0 Fox body Mustang.

Time takes it’s toll on all things including the wiring harness. In the case of Project Rehab, the wiring harness was not only showing the telltale danger signs of crunchy wire insulation, but had also been the victim of some very bad wiring repairs in the past. To get our mess of wiring straightened out we turned to the experts at Ron Francis Wiring.

Rehab’s 20-plus year old wiring harness after removal from the car. There are miles of wiring here, much of which aren’t necessary for our application.


You don’t typically think of these cars as being old like you do with the classic Mustangs, but the fact of the matter is that at over 20 years old, the wiring in these cars is showing its age, especially over time as it has passed through different ownerships

“You don’t typically think of these cars as being old like you do with classic Mustangs, but the fact of the matter is that at over 20 years old the wiring in these cars is showing its age,” says RFW’s Scott Bowers.

We wanted to replace the complete body wiring harness in Project Rehab, and at the same time upgrade the system, and eliminate a lot of unnecessary clutter in the process. What this will do is not only bring Rehab’s wiring up to modern standards, it will also avoid confusion should we need to diagnose a wiring problem. As the project progresses our new system will also allow us to safely add on to the electrical system for items like electric fans and nitrous. The end result reduces the amount of wiring in the car by eliminating circuits that our street/strip Fox just doesn’t need.

Poor repairs by previous owners, years of degrading, aging insulation, and connector pins falling out of their plastic housings are all common problems with older cars.

Expressing It

We had Ron Francis Wiring put together one of their Express wiring systems. This system includes a 16 fuse 18-20 circuit fuse panel which centralizes all of the wiring for the vehicle. “This really simplifies the installation of the wiring kit because we make the wiring kit in a modular design,” says Bowers. All of the wiring, relays and fuses are centralized to one point on the car simplifying installation and troubleshooting.

The Express wiring kit comes complete with a panel, color coded and screen printed wiring, and full easy to follow instructions plus RFW’s outstanding phone and email tech support.


This approach makes for a straight-forward wiring job and it also allows for easier troubleshooting down the road.“It really allows the customer to come to an understanding of what they’re doing.”

The Express panel centralizes all fuses and relays for the body harness and primary electrical system of the car. Every connection has a letter or number and corresponding color code which match the wire that will connect to it.

Included in every Express kit is a full color wiring schematic.

Know Your Alphabet

Express kits include the wiring packaged in alphabetically labeled bags. Each bag contains different sets of wires and a set of instructions. An analogy that kept popping into our heads as we proceeded through the project was that of building a scale model car, or constructing from the instructions in a LEGO set. You essentially started building the wiring harness by using the bags in alphabetical order. There were some things that we weren’t sure about at first, like how to tie in different circuits in the harness that needed a signal such as our turn signals, but that all came together as we performed the installation.


First wires to be installed are in bag AF for the alternator.

Of course each wire is color coded and screen printed every five-inches. There are no striped wires, and the colors of the wires usually reflects which spot on the Express fuse and relay panel that the wire connects to. The panel itself if also numbered, color coded, and lettered to match the wires being used with it and the customized instruction sheets.

Left: The Express panel can be mounted anywhere in the car that is shielded from moisture and dirt. We mounted ours to the transmission tunnel on the passenger side for easy access, but it could as easily been placed inside the dash or another location. Right: Reproduction OEM connectors are a specialty of RFW and many were included in our kit making the job that much easier.

Making Connections

Our only call to tech support was regarding wiring the Fox body’s rather unusual headlight switch. RFW emailed us a color schematic based on our needs within 24 hours.

Another cool thing about working with RFW was their ability to include certain reproduction connectors for our harness, including connectors for our turn signal/multi-function switch, and ignition switch. This literally made installing those components plug and play, with only the need to shorten some wires before the fuse panel and add the appropriate ends.

We did have to source a few headlight and tail light sockets from our local parts store, however wiring those up was easily handled with the labeled harness.


Installing It

For most people this job will take about two days to complete. It only took us about 30 minutes to pull the old factory harness out of Rehab, discovering all manner of potential wiring problems along the way. We followed the directions precisely, and even made a quick call to tech support to get some help on our headlight and dimmer switch connections in order to ensure we would have high and low-beam operation.

Top Row: Left: RFW screen prints their wires every five inches from end to end for easy identification. Center Left: We used electrical tape to bundle wires that were running side by side together, making them easier to wrap in conduit later. Center Right: The reproduction ignition switch connector fit just like the original and took any guess work out of wiring this critical circuit. Right: As each circuit is wired and connected the panel slowly fills with wires. Bottom Row: Left: Our Express panel fully connected after installation. Center Left and Center Right: We used friction tape and plastic conduit of various sizes to tidy up our installation and protect the wires. Right: We also took this opportunity to hide wires such as these for the headlight circuit routed outside the engine compartment and through the inner fender structure to conceal the wires.

Some things to bear in mind when installing this are first that this is not meant to be a direct, replica, replacement harness. Instead this is a custom install that will replace the factory harness. How this harness routes, connects, and fits in the car is up to the installer. Good grounds for each circuit are imperative to getting everything working right. Attention to detail and using quality methods and connectors when performing the installation will help as well.

If all of our installations went this easy, we could probably build complete project cars in a matter of weeks, rather than months. We know in the future whether we’re rewiring a complete car, or just adding an accessory, Ron Francis Wiring will be our first call.