Mopar Muscle - - Contents - TEXT AND PHO­TOS: JEFF SMITH

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.

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