TIPS FROM THE PROS ON HOW TO MAKE THOSE ELECTRICAL CONNECTIONS
Tips from the pros on how to make those electrical connections
It’s a common problem. You’ve spent the coin for a latemodel Hemi conversion, dropped even more on paint, tires, and wheels. But after a few test flights, it becomes clear something is amiss. The battery won’t stay charged, the turn signals are lethargic, and none of the original instrument cluster gauges function. The clues continue to stack up — it’s time for a new wiring harness.
In this case, we’re dealing with an otherwise fantastic car. It’s Chris Jacobs’ ’68 GTX that was originally a 440 car, but is now blessed with a 392ci Mopar crate engine. While the car moved under its own power, electrical functionality barely improved beyond that. It was time to call in professional help. The car landed at Shannon Hudson’s Redline Gauge Works in Santa Clarita, California, where Hudson summoned his friend Ken Myers, sole proprietor of Jetson Electric. Myers flew in from his home base in Washington state to flourish his magic wire crimpers over an American Autowire harness installation and make the world safer for democracy and GTX roadworthiness.
Myers card should read “Have Crimpers — Will Travel.” He’s like a hired gun who flies in and vaporizes all those electrical gremlins equipped with nothing more than a small bag of tools and a selection of slick electrical techniques up his sleeve. We tagged along shooting photos and extracted a few notable tips, while he meticulously rerouted wires, eliminated poorly executed electrical rat’s nests, and generally restored modern currency to the underdash area of this GTX.
Redline also contributed to this rebuild by adding functionality. When the car arrived, the interior included a three-gauge voltmeter, oil pressure, and water temperature panel in the dash. Both Redline and Myers agreed that the interior would be cleaner without these gauges and all (except the oil pressure gauge) were
already in place in the instrument cluster. Redline exchanged the factory ammeter with a voltmeter (which is far more useful) and rescaled the temperature gauge. The tach was there previously, but now would be updated with a higher-quality Speed Hut unit that uses a stepper motor controlled by software that interprets the late-model engine pulse without the need of a tach filter or adapter box.
Myers’ approach to wiring any car is both simple and effective. He prefers to minimize the number of connections between the power source and the load — like the headlights. As an example, the back side of the factory Plymouth instrument panel uses a printed circuit board connected to a round, 11-pin connector. While most backyard builders would clip the factory wires about 6 inches from the connector and use a handful of butt connectors, Myers preferred to use a special 12-pin connector called an AMP Mate-n-lock that he buys from Digi-key to use as the junction between the main harness and the cluster. Plus, he included additional length that allows extending the cluster a few inches from the instrument panel for maintenance. Simple ideas like that are what separate the pros from the amateurs.
Myers likes this generic 13-circuit American Autowire kit because, among other features, it includes new plastic headlight connectors. The American Autowire kits all use the better GXLXLPE wire. Using a dedicated crimping tool, you can make the female and male 56-series terminal connections very easily. The alternative is to reuse the old headlight connections spliced with butt connectors. Myers avoids this for obvious reasons. Have you ever banged your fist on a headlight to make the light work? That’s usually because the terminals are corroded. Plus, butt connectors add an additional electrical connection. In Myers’ world, neither of these is acceptable.
As an interesting twist, he also added twin-wire light sockets to the car’s side marker lights and isolates the ground from those sockets, moving the ground to the wiring. He then connects the positive side to the turn signal wire for each corner. Using an 1895 two-pin bulb with an isolated ground, the side marker lights blink off-sequence (they go out when the turn signal bulb is lit) when the turn signals are energized.
“When the wiring you don’t see needs to look as good as the welds you don’t see.” — Ken Myers, Jetson Electric
Another feature Myers likes to include is LED courtesy lights pointing down from under the dash that illuminate with the dome light that’s also converted to LED. To make an unsightly bundle of wires look better, he often looms wires using unsplit Techflex braided looms. Myers prefers using the unsplit braid, because it looks better. But this means the wires must be covered before they’re terminated. Another tip is that he always cuts this braided loom with a heat knife, so the weave doesn’t fray, and then uses heat shrink on the ends to cleanly terminate the loom. He also prefers the heat shrink with internal adhesive — it holds better than nonadhesive style. These materials are available through a company called Waytek Wire. Finally, he uses cloth tape to bind wires together instead of black electrical tape, because it eliminates the sticky residue. He also occasionally wraps wire bundles with this tape.
These are just some of Myers’ tips — it’d take a book to include them all. Once completed, the GTX’S factory functionality returned, and the world seemed like a better place. Hudson even commented that he thought the engine even ran smoother now with a cleaner electrical signal. While that would be difficult to confirm, it’s true that this GTX is now electrically sound and far more road worthy.
This is the interior side of the bulkhead connector, and that large frayed and fried wire is the main power feed for the interior side.
This jumbled-up mess is what was controlling the electrical system and door solenoids. A previous hacker didn’t bother to use dedicated relay connectors, but instead relied on individual with exposed connectors. Shame …
American Autowire’s harness is the one Ken Myers prefers to work with. This particular harness is a generic 13-circuit GM harness that offers numerous advantages, such as minimizing the number of connections and using late-model-style fuses.
Myers mated the wires into the cluster (instrument lights, turn signals, voltmeter, gas gauge, and others) to a white, multi-pin connector. This leaves the original round cluster connector in place, yet provides a more robust and accessible disconnect that can be seen next to the steering column. This also avoids an ugly collection of nine separate butt connections.
This is the stock Mopar 11-pin connector for the instrument cluster. Myers retained this connector, leaving roughly a 6-inch length of wire off each pin.
This is a properly crimped female terminal that’s used throughout the American Autowire harness. This requires a specific single-wire crimping tool that American Autowire sells (PN 51085). They also offer a rental program if you’re likely to only use this tool for a single rewiring effort. Instead of running through the multiple steps on how to perform this operation, there’s a very informative video on American Autowire’s website on exactly how to perform this operation.
Myers provided this schematic to show how he rewires the side marker lights using 1895 bulb dual terminal light fixtures to replace the single wire lights. With the dual terminal lights wired as shown, the side marker lights will alternate flash with the turn signals, but still operate as standard side marker lights.
You might recognize the GTX’S owner – Chris Jacobs (middle). He was the host of the Overhaulin’ television show for many years. On the left is wiring pro Ken Myers with Redline Gauge Works owner Shannon Hudson on the right.
One of Myers’ subtle additions is to use underdash LED courtesy lights that are matched to the dome light. He purchases these separately, usually on Amazon. He also likes those trick USB power ports that can be placed in the glovebox to recharge a cell phone or power up a music source.
Redline’s Service Manager Andres Ceron disassembled the original cluster, converted the ammeter to voltmeter, installed a new Speedhut tach stepper motor, calibrated the tach, and also re-soldered the 9-pins in the circuit board to improve their durability.