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3G Alternator wiring and the dreaded Ammeter.

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Eliteman76 View Drop Down
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    Posted: 22-June-2022 at 12:52PM
Having a conversation the other day with Chuck reminded me of the fact, I have been running my car for years with a 3G alternator...and having no clue if my ammeter is working or not.

Also brought to my mind the whole fuseable link situation and fire risks.

Because my 3G decided to eat the sliprings, I need to repair my alternator. I am no looking into info specifically regarding the 72-73, and 74-76 cars and what is the proper way to shunt/bypass the ammeter.

I need to pull my dash apart, and I am looking at waiting to get rid of the ammeter, or at the least completely disable the circuit but wondering if this will affect other circuits.
Andrew: Long time Torino guy and GTS.ORG admin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 22-June-2022 at 2:24PM
IIRC, if you get rid of the ammeter shunt wiring, you will have to move all the electrical terminals from the remote electrical stud to the battery side of the starter solenoid. The remote electrical stud is supplied voltage directly from the alternator and indirectly from the shunt wiring, everything attached to the remote stud will show electrical loads on the ammeter(like blower motor and/or headlights) when engine is off. The shunt is basically a calibrated piece of 10ga wire/cable with two smaller sense wires, one attached to the battery side of the starter solenoid and one wire attached to the remote electrical stud, with both wires running and attached to the back of the ammeter where it senses the electrical flow/electrical loads between the battery and the alternator. That 10 ga wire is WAY too small for a 130 amp alternator. You could try to use a 4ga cable for the shunt, but you are still dealing with a gauge that pegs out at 65 amps, about half the output of a large cased 3G. Hope this is helpful.
www.supermotors.net/22468
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72 RS 351 Quote  Post ReplyReply Direct Link To This Post Posted: 22-June-2022 at 2:53PM
I would also like to alter the wiring for the ammeter. I'll change it to a voltmeter for my keeper vehicle, but the one I sell I'd prefer to leave it close to OEM/stock.

Question, who might be good to ask about possibly mounting an alternator in the place of a 4G model, which makes less than 80 amps? I have a special LiFePO4 battery which is made for a group 24 hold down and tray, but can only handle 80 amps of a 12v car alternator. It works great for long period storage, has an 11 year warrantee, but it takes special care to charge it separately, plus that in car limitation. I'm going to adapt a late model(96-01) bracket set, which is made for a 4G alternator(three bolts in the same plane). I wish a 3G could be built down to that 80 amp level, because I want a 3G instead of the 4G for two other projects(the 4G is expensive to repair, and the 3G has tons of support for varying amperage, plus cheap to repair).
Don
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eliteman76 Quote  Post ReplyReply Direct Link To This Post Posted: 22-June-2022 at 4:08PM
Todd, wonder if you might have some info.
So, my 3G was a custom unit.
My memory while foggy about some things, distinctly recalled the fact my 3G bridge rectifier is a 140amp.
The voltage regulator is a HD variant with a F77U-10316-AA motorcraft part number. 
What cracks me up is...looking at the voltage regulator, the brushes seem tiny. I also noticed on the wear of the slip rings, the brushes were not centered on the rings. Offset.

I am currently looking for an actual alternator / starter repair shop. 
I know I should just get a new 3G but I just want to fix my unit instead of buying new.

Also, just as some background. I went with to a large power feed wire. At least 4 guage, off the 3G. I took the original 3G feed wire and turned that into the ground from the case to my common grounding point. 

I have my new CVF Wraptor system that I really need to install, but I don't feel like disturbing my AC system until this fall so I need to fix my 3G for the time being.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72 RS 351 Quote  Post ReplyReply Direct Link To This Post Posted: 23-June-2022 at 1:34AM
The 3G alternator is the best IMO for anything it was installed in. The cases keep changing over the years with new mounting designs, so not many can be swapped to other applications. The 3G began with the older alternators that mounted with two bolts and one was used for the adjustment. That style is the easiest to retrofit into tons of older cars, simply if the bolt spread matches the bracket on the engine.
Don
73 Ranchero Sport "72 front end", floor shift/console, planning EFI 7000rpm 351-4V &4R70W
73 Ranchero GT 351C-4V 3.70 gears for sale later.
92 Lincoln Mark VII SE, OBDII 347/4R70W
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Post Options Post Options   Thanks (1) Thanks(1)   Quote aquartlow Quote  Post ReplyReply Direct Link To This Post Posted: 23-June-2022 at 8:40AM
Wish you were closer, we could rebuild what you have. I find them at U-pull-it yards for $30 in recent rebuilt condition. Once purchased I remove the rectifier/voltage regulator and install an upgraded rectifier(Registar RF-053HV) along with a Transpo F794HD voltage regulator. Usually the white regulator have an LRC delay, meaning that they delay the alternator from charging during or just after start up. I always use the gray or black VR's which do not have LRC(Load Response Control). The brushes on a 3G are somewhat on the thin side, but I don't believe there are any other options. The slip rings are replaceable, just use the old ones as a guide to where you would like the new ones, so they can more or less be centered.  
www.supermotors.net/22468
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eliteman76 Quote  Post ReplyReply Direct Link To This Post Posted: 23-June-2022 at 12:04PM
I appreciate that Todd. Iended up finding a company out of Kansas City called C&C Starters and Alternators. They are a bulk seller of alternator and starter parts and stock a lot of stuff for 3G alternators. I debated about snagging a junkyard alternator for $25, but I got a new rotor assembly for the 130amp, and two voltage regulators and two brush holders, and a couple new case bolts. I figure I can take the rotor and set it aside for the time being. 
I'll have my parts delivered tomorrow so I can work on getting my alternator redone this weekend. These guys are also one of the biggest amazon sellers for alternator/starter parts evidently. Spent less with them, vs buying parts off Amazon!
Always nice being able to talk with local folks.

My main concern now is dealing with the ammeter situation to make sure of things.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72FordGTS Quote  Post ReplyReply Direct Link To This Post Posted: 24-June-2022 at 2:01AM
Andy, can't you just ditch the Ammeter and convert the gauge to a voltmeter?  I know there have been folks on this forum who have done that in the past.  I know we have some info on past posts and dealing with ditching the ammeter shunt wiring and converting to a voltmeter.  

RocketMan does Ammeter conversions.  He might have some knowledge on dealing with the shunt wiring:

Vince

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