Nothing Shocking - Rewiring a 1951 Plymouth Wagon

Does the word electron intimidate you? Do your eyes glaze over when people start talking about voltage, amps, or direct current? Does the term butt connector make you giggle uncontrollably? Well, don't fret, you're not alone. If nothing else, the ROD & CUSTOM staff is right there in the same boat with you.

Fact is, most hot rodders are unfamiliar with electricity. The good news is that it doesn't matter. Over the past dozen years or so, the street rod aftermarket has done an excellent job of simplifying automotive wiring. These days you can choose from any number of do-it-yourself wiring harness kits, all of which are designed to make rewiring a straightforward--dare we say, easy--process. You no longer need to be an electrical genius to tackle the job. In fact, you don't even have to know how or why all the stuff works. All you really need is to be patient and follow instructions to get the job done in a tidy, professional manner.

Skeptical? Hey, that's understandable., which is why, to set your minds at ease, yours truly was assigned to do this story. You see, prior to this, my automotive electrical experience was limited to installing a few stereos and other basic accessories. Rewiring an entire car was as new to me as I'm sure it is to many of you.

The guinea pig for this experiment was my '51 Plymouth wagon, which turned out to be a great candidate. As you might expect, 50-plus years of service and exposure had left the original cloth-covered wiring in questionable shape. Everything was still functioning (most of the time), but there were bare, frayed wires everywhere, not to mention funky splices and creative connections administered by the previous owner. To top it off, the car was still running on a positive-ground 6-volt system, and I wanted to convert to 12-volt negative-ground to take advantage of newer accessories and a possible drivetrain swap in the future. Upgrading to fresh wiring and a modern fuse panel seemed like a good idea.

The wiring kit for this project came from EZ Wiring and, as the company name implies, was designed with the do-it-yourself hot rodder in mind. EZ Wiring actually offers several styles of pre-wired fuse block kits, along with a variety of electrical accessories (plugs, switches, etc.). We elected to use the company's new EZ 20, a 20-circuit kit with a compact fuse panel designed for cars where space is at a premium. Even though the Plymouth isn't exactly short on space (especially compared to, say, a Model A roadster), the idea of a compact panel was still appealing.

Like many aftermarket wiring kits, the EZ harness uses a GM-style color coding system (kits with all-black wires are also available), and each wire is labeled every 5 inches to simplify installation. The ignition and headlight switch wiring are also designed to plug right into GM-style switches. The kit comes with the necessary flashers, a horn relay, GM-style column connectors, and the most important accessories, instructions and diagrams.

All told, the installation went quite smoothly--a little time-consuming and tedious, perhaps, but that's the nature of wiring. The biggest hangups came from working on a "finished" (or assembled) car, which meant maneuvering around obstacles, cramming my hands (and sometimes body) into tight spaces, and taking time to move and remove parts (interior panels, sill plates, carpet, etc.) to route wires where I wanted. Retaining the Plymouth's stock switches and instruments also presented a few challenges, but nothing that couldn't be overcome with a little rodding ingenuity (and by consulting the OEM electrical diagram in the car's service manual).

Wiring may not be the easiest or most fun part of a hot rod or custom car project, but it's always necessary, so you might as well learn to do it yourself. In addition to saving money and gaining a sense of accomplishment, you'll become a lot more familiar with your electrical system, making it easier to troubleshoot in the future. Even if you're not an electrical genius when you start, you may just feel like one when you're finished.

SIX TO TWELVE
As mentioned in the text, my rewiring adventure also involved converting the Plymouth over from a 6-volt, positive-ground system to 12-volt, negative ground. There's not enough space to adequately address the topic here, so I'll recommend the 20-page tome I used as a crib sheet -- "The Official 12-Volt Conversion Guide," by Randy Rundle. My copy came from Speedway Motors. Meanwhile, here's a quick-hit list on this particular conversion:

* Replaced the generator with an alternator.
* Installed a 12-volt voltage regulator.
* Swapped the 6-volt starter solenoid for a 12-volt unit.
* Replaced the 6-volt coil with a 12-volt coil.
* Changed all 6-volt bulbs to 12-volt.
* Installed a voltage-drop unit (Runtz) on the fuel gauge.
* Reversed wires on the amp gauge (so it will read correctly with a negative-ground system).
* Installed a 12-volt battery (sounds obvious, but you never know!).
* The car currently has no heater, so I didn't have to worry about the blower motor. The wiper motor will be replaced with a 12-volt, negative-ground unit.

TOP 10 WIRING LESSONS

1 Measure twice, cut once.
2 Read the instructions. Twice.
3 Wiring harnesses are like old cars--they usually need to be customized to fit your needs.
4 Pulling on the wires won't make them longer.
5 Measure twice, cut once.
6 You'll wish you had swinging pedals after wedging your neck between floor-mounted brake and clutch pedals while lying on your back under the dash.
7 Face it, the street rod world is Chevy biased. Wiring is easier when you use GM-style switches, columns, and alternators.
8 Zip-ties are your friends.
9 We don't care about your adult-onset attention deficit disorder--finish one section before moving on to another.
10 Measure twice, cut once.