Alternator upgrade
Lead Driver
Joined: Jun 2013
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From: Tolland, CT
Logistics Pro
Joined: Jun 2017
Posts: 3,952
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From: Edmond, OK
A 3G 1 wire alternator from a 94 
Taurus fit on the 6.9l IDI in my 86 Bullnose truck perfectly. Here's a good write up.
https://www.garysgaragemahal.com/3g-conversion.html
Taurus fit on the 6.9l IDI in my 86 Bullnose truck perfectly. Here's a good write up.https://www.garysgaragemahal.com/3g-conversion.html
Cargo Master
Joined: Mar 2008
Posts: 2,564
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From: Washington
Or would you be willing to also extend the small green wire from the voltage regulator mounted near the battery, to the new alternator?
Also if you looking for advice, it would be helpful if you shared why you are doing this.
Did the 1G alternator fail?
Are you looking for a higher output alternator for some reason?
Do you have an AMP METER that you want to keep functional?
1 wire alternators are a modified alternator. Each builder / modifier does it differently.
So it difficult to compare them or to really know how it will work, do you have to increase RPM to bring it online?
I would only use a one wire alternator on a old tractor that didn't have any electrical system or wiring, just some to run the headlights and to keep the battery charged.
Another problem is if you break down on the road, auto parts store don't have them.
Jim
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Joined: Jan 2001
Posts: 56,977
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From: Virginia
A one wire alternator is not really a upgrade. And if you have a failure, good luck finding one in a store somewhere. But they are a alternative, just pick one and try it. We do not see them much on here, maybe because they work well? I do not know.
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Cross-Country
Joined: Nov 2025
Posts: 57
Likes: 3
The reason is im tired of dealing with the alternator not charging the battery in another post i thought and hoped it was the regulator but its problem lie in mess of wiring that is has and I just want to simplify it for now
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Cross-Country
Joined: Nov 2025
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Lead Driver
Joined: Apr 2002
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Battery might not charge for several reasons. How do you know your regulator works or not? Battery could be dead, connections poor and dirty. Assuming you replaced it with gnew, doesn't mean it's good. No gnew wasn't a misspell. Many regulators reported bad out of the box. The 1G alternator is old school cool. Should work great, plug and chug. What makes you think the wiring is a mess. Some of these trucks come with a ratsnest of wiring and vacuum tubes from the factory.
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From: Virginia
Just pick one and try it then. If they make one to exactly fit your truck and bolt on. If you can't find one that bolts on and requires modification, you might as well buy a older GM alternator and install it. It's very simple to hook up, it has two wires. One thick one to charge the battery, and one smaller one that the green/red Ford wire hooks to. It's what I am running on my Bronco II. Many many tractors and equipment use that style GM alternator also. It is what my Case backhoe has on it.
FTE Legend
Joined: Nov 2015
Posts: 30,876
Likes: 4,116
From: Angier, NC
When you say... "1 wire alternator" are you just referring to the large output wire?
Or would you be willing to also extend the small green wire from the voltage regulator mounted near the battery, to the new alternator?
Also if you looking for advice, it would be helpful if you shared why you are doing this.
Did the 1G alternator fail?
Are you looking for a higher output alternator for some reason?
Do you have an AMP METER that you want to keep functional?
1 wire alternators are a modified alternator. Each builder / modifier does it differently.
So it difficult to compare them or to really know how it will work, do you have to increase RPM to bring it online?
I would only use a one wire alternator on a old tractor that didn't have any electrical system or wiring, just some to run the headlights and to keep the battery charged.
Another problem is if you break down on the road, auto parts store don't have them.
Jim
Or would you be willing to also extend the small green wire from the voltage regulator mounted near the battery, to the new alternator?
Also if you looking for advice, it would be helpful if you shared why you are doing this.
Did the 1G alternator fail?
Are you looking for a higher output alternator for some reason?
Do you have an AMP METER that you want to keep functional?
1 wire alternators are a modified alternator. Each builder / modifier does it differently.
So it difficult to compare them or to really know how it will work, do you have to increase RPM to bring it online?
I would only use a one wire alternator on a old tractor that didn't have any electrical system or wiring, just some to run the headlights and to keep the battery charged.
Another problem is if you break down on the road, auto parts store don't have them.
Jim
The problem is the ALT can not sense the voltage at the battery where it needs to, it senses it right at the large output post
So the ALT thinks the battery is charged because it sees voltage at the stud but the battery is really 11 volts and not charging.
If you dont have any high electrical demand then there is no need to change what you got.
Being a F100 it is not a 4x4 so no plow.
I pull a 20' enclosed trailer with my 81 F100 in the dark a lot of times and it had electric brakes on both axles and the factory ALT works just fine for the last six years.
Dave ----
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Cross-Country
Joined: Nov 2025
Posts: 57
Likes: 3
I found a place for replacement harness for it so ill give that a shot but the harness is in bad shape and the some of the wire have no current i did replace the 2 circuit breakers and its starts a better but no charge to battery
Lead Driver
Joined: Jun 2013
Posts: 5,654
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From: Tolland, CT
https://www.garysgaragemahal.com/1981-evtm.html
Tuned
Joined: Dec 2024
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From: Texas, near Houston
Logistics Pro
Joined: Jun 2017
Posts: 3,952
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From: Edmond, OK
^^^THIS^^^
A 3G alternator isn't 1 wire, but it deletes the external voltage regulator.
The 3G alternator I put on my Bullnose truck has performed much better than the 10SI 1 wire alternator I put on my 71 Oldsmobile.
A 3G alternator isn't 1 wire, but it deletes the external voltage regulator.
The 3G alternator I put on my Bullnose truck has performed much better than the 10SI 1 wire alternator I put on my 71 Oldsmobile.
FTE Legend
Joined: Nov 2015
Posts: 30,876
Likes: 4,116
From: Angier, NC
I just dont see the need for the 3G if you dont have extra electrical load than what the factory had 
If you drive it long enough to put back into the battery what you pulled out from starting even with the head lights & heater on you will not have a problem.
Going on 6 years now without a dead battery from the 1G ALT.
Dave ----
If you drive it long enough to put back into the battery what you pulled out from starting even with the head lights & heater on you will not have a problem.
Going on 6 years now without a dead battery from the 1G ALT.
Dave ----