Marc Christ
Brand Manager, Modified Mustangs & Fords
April 16, 2014
Photos By: Kristian Grimsland

Project cars are a lot of fun. Getting your hands dirty in the garage on evenings and weekends with handtools and friends can be very rewarding—until you have to do wiring. It seems to be the one thing that everybody hates.

But why is that? Is it because it is misunderstood? Or is it because it's tedious and time-consuming? Maybe it's a little of both, but there are ways to minimize the headache.

Read A Book

Unless you're an engineer (or an electrician), you probably don't enjoy wiring anything, especially cars. And you probably don't like reading instructions or manuals. But all of the wires look the same, so you don't know where they go without a schematic (or diagram). Wiring diagrams take away the majority of the unknowns when it comes to automotive wiring. You can see the routing of the wire and its function.

Dealerships have shop manuals that are filled with model- and year-specific diagrams, which aren't typically available to Joe Mechanic. But aftermarket repair manuals like Chilton and Haynes are readily available at auto parts stores and online. These are a must-have when taking on a major wiring project. One will set you back $10-15, but they're well worth it. They also provide helpful info like torque specs and fluid capacities.

Since almost everyone has a computer and Internet access now, and most on our phones, finding wiring diagrams online can be a quick and easy way to solve an immediate wiring problem. Just type your year, make, model, and "wiring diagram" into the search engine, and you'll be surprised how quickly your questions will be answered—for free! Plus, if you're having a wiring problem, you can also type in the year, make, model, and symptom in the search engine, and may be able to solve your problem that way as well.

Have A Plan

If you fail to plan, then you plan to fail. This doesn't ring any more true than when you're dealing with an automotive wiring project like ours. You need to write down all of the systems that you need, where the inputs are (sensors and switches), and where they go (lights, solenoids, electric motors, etc.). It might even be a good idea to do all of this on a bird's eye drawing of the car itself. You don't have to be an artist to do this, just draw a rectangle.

Figure out what kind of wire harness you need, and don't go overboard. For instance, we ordered a very generic eight-circuit modular harness for our Coyote Coupe, seen in the photos on these pages. This car is equipped with headlights, taillamps, turn signals, horn, wipers, and even A/C. Heck, we even have a circuit leftover for a radio, which we'll probably install later. In other words, keep it simple. The more circuits you get, the more hassle you get.

You need to go ahead and have your engine and engine controls choices made, purchased, and installed. It's much easier to splice everything in this way, and it will make for a cleaner finished product. This goes for gauges, too. You'll see what we did with our gauges in the included photos.

Take Your Time

If there's one single mental tool that you need for a project like this, it's patience. Check, then double check, to make sure you have routed the wires correctly, and that they won't interfere with any other system. Hopefully, this will be the only time you'll have to do this, so go slow and do it right the first time. You'll be glad you did.

1. Summit Racing Equipment sent us this 8-circuit universal harness (PN PRF-10307; $325.97) by Painless Performance. This modular harness features eight full circuits, and is ideal for race cars or simply built street cars, like ours.
2. There are plenty of ways to tackle a wiring project, but the only way to start is by reading all the material you can. We read the instruction manual that came with the Painless harness, the instructions for our FRPP Coyote controls pack, the manual for our Classic Auto Air system, and the shop manual for ’85 Mustangs.
3. After determining where our fuse panel would best serve our needs (under the dash in the stock location), we welded a bracket to the dash brace.
4. Then we bolted the fuse panel to the new bracket.
5. We then bolted the bracket back in place.
6. The next (and possibly most tedious) step in the process was to trace and label all of the connectors from the original harness that we were going to use.
7. To do this, we used the Ford shop manual for the car (you could use a Chilton or Haynes manual) to identify the wires, and then labeled them using the provided labels and masking tape with a permanent marker.
8. We left the pigtails plenty long and bundled the wires together with electrical tape.
9. We then routed the new harness, being sure to leave plenty of extra for splicing.
10. Then we cut the excess harness.