Ford Al­ter­na­tor Up­grade

Charge Into the 21st Cen­tury With Ford’s Late-Model 3G Al­ter­na­tor

Hot Rod - - Front Page - Mar­lan Davis

In­tro­duced in Au­gust 1964, Ford’s first-gen­er­a­tion Model 1G al­ter­na­tor was a real step up in re­li­a­bil­ity and cur­rent out­put com­pared to the old-school gen­er­a­tors it re­placed. Orig­i­nally avail­able in rat­ings rang­ing from 38 through 60 amps, the 1G was at best barely ad­e­quate when the elec­tri­cal sys­tem was brand new and most cars only had a ra­dio, a heater, wind­shield wipers, light­ing, horns, and a points ig­ni­tion sys­tem. But with an ag­ing, un­der-wired elec­tri­cal sys­tem and to­day’s typ­i­cal hot rod add-ons like elec­tric fuel pumps, fuel in­jec­tion, high-out­put ig­ni­tion sys­tems, Halo­gen head­lights, power win­dows, and air con­di­tion­ing, those lazy 1G al­ter­na­tors and their crude sep­a­rate volt­age reg­u­la­tors aren’t up to the job. Frankly, other than a straight resto, it’s time to put them out to pas­ture in fa­vor of mod­ern, high-out­put al­ter­na­tors with in­ter­nal reg­u­la­tors.

For many years, a pop­u­lar so­lu­tion for old Ford ve­hi­cle own­ers that needed more amps was adapt­ing an in­te­grally reg­u­lated GM al­ter­na­tor for use on a Ford. GM climbed on the high-out­put, in­te­grally reg­u­lated al­ter­na­tor band­wagon far ear­lier than Ford, in­tro­duc­ing its re­li­able, first-gen­er­a­tion “10-SI” al­ter­na­tor as an op­tion on some cars in 1969 be­fore it be­came stan­dard equip­ment on all of the Gen­eral’s ve­hi­cles by 1973.

Play­ing catch-up, Ford didn’t come out with its first in­te­grally reg­u­lated al­ter­na­tor un­til 1982, when the model 2G al­ter­na­tor ap­peared. The 2Gs were of­fered stock in 65- and 75-amp rat­ings, but they had re­li­a­bil­ity is­sues even in bone-stock­ers.

In 1994, Ford fi­nally hit a home run, in­tro­duc­ing the 3G in­te­grally reg­u­lated al­ter­na­tor that re­mained in use on some Ford ve­hi­cles well into the 21st cen­tury. Up to 200 stock amps are avail­able with some vari­a­tions; 130-amp ver­sions ex­ist that still have di­rectly op­posed mount­ing ears that per­mit them to phys­i­cally bolt right into place of that old model 1G us­ing the ex­ist­ing 1G brack­ets. Highly re­li­able and eas­ily adapt­able, the 3G has be­come the go-to al­ter­na­tor for Ford retrofitters.

Let’s take a closer look at the 3G, as well as what it takes to per­form a quick, typ­i­cal retro­fit into a 1960s clas­sic Ford, cour­tesy of Ad­vanced En­gi­neer­ing West’s Mark Sanchez. We’ll be us­ing qual­ity Au­toZone-re­man­u­fac­tured al­ter­na­tors, plus a late-model Ford OE 3G har­ness scrounged from the wreck­ing yard. Sanchez’s pre­ferred method of wiring the 3G up just like a Ford stocker lets you go to any auto-parts store for a re­place­ment if the al­ter­na­tor takes a dump on a long-dis­tance cruise—some­thing you can’t nec­es­sar­ily do with those uni­ver­sal one-wire al­ter­na­tors.


For both 1G V-belt and most 2G ser­pen­tine-belt con­ver­sions, you want a 3G al­ter­na­tor with case mount­ing ears that are

180 de­grees op­posed (straight across from each other), with 6.900-inch bolt cen­ter­line spac­ing. Other 3G vari­a­tions with off­set ears or ears on one side of the case won’t work as di­rect re­place­ments. One 3G al­terna- tor con­fig­u­ra­tion meet­ing this re­quire­ment was orig­i­nally in­stalled on 1994–1995 Mus­tang V8s, 1994–1997 Thun­der­bird/ Cougar XR7 3.8L V6s, and 1994–2000 Mus­tang 3.8L V6s. Au­toZone’s re­man­u­fac­tured Du­ralast unit for this ap­pli­ca­tion is PN DL7734-6-11. Un­like sketchy wreck­ing-yard take-outs, Au­toZone’s Du­ralast al­ter­na­tors carry a life­time war­ranty.


Hooking up the new al­ter­na­tor re­quires com­ple­men­tary wiring that matches the new al­ter­na­tor’s con­fig­u­ra­tion and out­put, in­clud­ing late-model con­nec­tors and the proper 4- or 6-gauge pos­i­tive bat­tery (B+) charge wire. The orig­i­nal 1960s charge wire was usu­ally only 12-gauge and, at least on the 1966 Galaxie shown here, wasn’t pro­tected by any fusible link. The plugs and up­graded wiring are part of the junk­yard 3G al­ter­na­tor har­ness, which costs about $7 at the lo­cal Pick-A-Part yard. Any 3G al­ter­na­tor har­ness works; you don’t nec­es­sar­ily need one that specif­i­cally matches the rec­om­mended Mus­tang al­ter­na­tor con­fig­u­ra­tion.

Want to build your own har­ness in­stead? Del Mar Wiring is one source for the cor­rect 3G-type con­nec­tor and pig­tail as­sem­bly. Sanchez at AEW has orig­i­nal Ford con­nec­tor bod­ies and ter­mi­nals if you want to start en­tirely from scratch. Due to the 3G al­ter­na­tor’s high out­put, use AWG-4 or AWG-6–sized wire pro­tected by dual 14-gauge fusible links or a 150- or 175-amp mega fuse for the main al­ter­na­tor “BAT” stud charge-wire run­ning back to the starter so­le­noid.


It’s a bet­ter than even chance the new al­ter­na­tor case shells will re­quire reclocking so the con­nec­tions end up in the right ori­en­ta­tion for your spe­cific in­stal­la­tion. Both early and late Ford cases are held to­gether by three bolts, so there are three pos­si­ble clock po­si­tions. For the Ford-style al­ter­na­tor, we’ll de­fine the clock po­si­tion as “read” look­ing from the rear of the case for­ward. The amount of “clock­ing” is the off­set in imag­i­nary old-style ana­log “clock hours” be­tween the case’s small “ad­juster ear” and the bat­tery-stud ter­mi­nal and/or main con­nec­tor, with the small ad­juster ear fac­ing straight up (“12 o’clock”). What’s a lit­tle con­fus­ing is that on most clas­sic Ford mus­cle cars, the 1G al­ter­na­tor ad­juster ear faces straight down as in­stalled on the stock brack­ets, while on the 180-de­gree-op­posed 3G late-model stock ser­pen­tine-drive in­stal­la­tion, the ad­juster ear mounts straight up—but we need to de­fine a com­mon ref­er­ence point to de­ter­mine the reclocking amount needed (if any).

For the 1966 Galaxie 352 shown in the pho­tos, the new al­ter­na­tor’s clock­ing

was way off as de­liv­ered, but cor­rect­ing it was a cinch: Un­like GM-style al­ter­na­tors, the in­ter­nal brushes on Ford units are un­likely to fall out when sep­a­rat­ing the front and rear shells as long as the cen­ter black ring el­e­ment doesn’t pull away from the rear case shell.


Late-model 3G al­ter­na­tors come equipped with ser­pen­tine-drive belt­com­pat­i­ble pul­leys, but the old Galaxie uses V-belts. We found that the V-belt pul­ley fit prop­erly on the 3G’s sup­pos­edly met­ric shaft, align­ing per­fectly with the car’s other pul­leys.


One prob­lem with GM al­ter­na­tor con­ver­sions is that most GM OEre­place­ment-style units need a diode or re­sis­tor spliced into the wiring if not run­ning an id­iot light. Other­wise, due to cur­rent back­flow, the al­ter­na­tor re­mains en­er­gized and the en­gine keeps run­ning, even when the ig­ni­tion key is turned to the “off ” po­si­tion! That’s be­cause, on the GM sys­tem, the warn­ing bulb also sup­plies the nec­es­sary re­sis­tance to shut down the sys­tem and avoid back­flow.

But this isn’t an is­sue with Ford al­ter­na­tors. You can run any combo of id­iot light, volt­meter, or am­me­ter with­out run-on prob­lems. It’s true the stock Ford id­iot light cir­cuit be­hind the dash has al­ways had (de­pend­ing on the model year) a 500- to 560-ohm re­sis­tor in par­al­lel to the bulb, but not run­ning the

re­sis­tor only causes the bulb to not turn off (it does not af­fect al­ter­na­tor shut­down). How­ever, we don’t rec­om­mend run­ning an am­me­ter be­cause of the 3G’s high out­put; con­vert to a volt­meter in­stead.


You can up­grade from a 60-amp (at best) 1G al­ter­na­tor to a mod­ern, re­li­able 3G 130-amp al­ter­na­tor for around $50 (us­ing a wreck­ing-yard al­ter­na­tor) or just un­der $200 (in­clud­ing a qual­ity re­man­u­fac­tured al­ter­na­tor). Even if your vin­tage ride doesn’t nor­mally de­mand a full 130 amps, the late-model al­ter­na­tor can—when re­quired— gen­er­ate 540 per­cent more amps off-idle (81 amps ver­sus 15 amps at 900 en­gine rpm). You’ll ap­pre­ci­ate that on a cold, stormy, dark night with your brights, heater/blower, and wind­shield wipers all run­ning full blast. An al­ter­na­tor only gen­er­ates the amount of amps when con­di­tions re­quire it, so hav­ing a huge “re­serve” ca­pac­ity that’s rarely used should re­duce the unit’s duty cy­cle, ex­tend­ing its use­ful lifes­pan. It may out­last the car.

“All amped up and ready to go where no old Ford has gone be­fore, Ford’s 3G al­ter­na­tor is easy to swap into older Fords.” — Mark Sanchez, AEW

[ Wide avail­abil­ity, high out­put, and ro­bust dura­bil­ity make the FordMo­tor­craft 3G in­te­grally reg­u­lated al­ter­na­tor the eas­i­est and best choice for re­plac­ing old 1G ex­ter­nally reg­u­lated al­ter­na­tors on amped-up mus­cle cars as well as later Fords stuck with a 2G al­ter­na­tor, in­clud­ing 1980s through early 1990s Fox-bod­ies.

0102 01–02] The 1G al­ter­na­tor ( left) was Ford’s first al­ter­na­tor. Ex­ter­nally reg­u­lated, it came on the scene in 1964 and sol­diered on through the mid-1980s. Cases may vary in ap­pear­ance. The 1Gs don’t have suf­fi­cient out­put, es­pe­cially at low rpm, to keep up with mod­ern high-cur­rent ac­ces­sories. Ford’s first in­te­grally reg­u­lated unit, the Model 2G ( cen­ter), served from 1982 through the early 1990s and had re­li­a­bil­ity is­sues. The more pow­er­ful and re­li­able 3G ( right) ap­peared in the mid 1990s.03–04] A 2G’s big­gest is­sue: an un­der-ca­pac­ity rec­ti­fier and power con­nec­tor ( A). The con­nec­tion and large, hol­low case cav­ity were cor­ro­sion-prone, which in­creased re­sis­tance, caus­ing volt­age drops and heat build-up. Re­sult: early unit fail­ure, and even elec­tri­cal fires. Some af­ter­mar­ket re­mans, like this Au­toZone unit ( B), have an in­te­gral one­piece rec­ti­fier and con­nec­tor as­sem­bly with larger wires, but at best it’s only a stop­gap so­lu­tion. The “ASI” con­nec­tor ( C) is the same as the one on the later 3G de­sign, but the reg­u­la­tor ( D) doesn’t in­ter­change.03 04FRONTREAR


15–17] Sanchez usu­ally grabs a com­plete al­ter­na­tor rear har­ness from any 3G-equipped Ford in the wreck­ing yard. The har­ness in­cludes the proper con­nec­tors, fusible links, and wire-gauge sizes for ev­ery cable. The plain green wire vis­i­ble in 17 came with this par­tic­u­lar take­out har­ness, but isn’t used or ter­mi­nated on typ­i­cal retrofits.

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