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3G Alternator Conversion with 1996 F150 Harness

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3G Alternator Conversion with 1996 F150 Harness

I was just reading the section on the 3G alternator conversion as I was trying to find out what size fuse holder and fuse I was going to need. Then I spotted Gary's note that the 1996 harness had a fusible link in the grey wire. I have the 1996 alternator harness, but the guy that pulled the engine cut the end of it off. There's currently only about 2" of it there. I don't think it was much longer to begin with. I saw one last weekend and it looked like it was only about 3" long to the ring terminal (the grey part, that is).

So should I still put a fuse on this? I assume yes?...
If yes, what size?

I don't know for certain, but from what little I've read, I believe the factory alternator on this engine was 95 amp?

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

The 1996 charging system is shown below, and it has a 12 gauge fuse link. But that begs the question of what size fuse to replace it with.

In the 1985 EVTM there's a note that says: Note: (Fuse Link D) 14 gauge with 70A alternator. 16 gauge with 40 or 60A alternator. So 12 gauge would seem to be about right for a 95A alternator. (The diesel must have gotten a much bigger alternator as it has two 12 gauge fuse links in parallel.)

Given that I'd say go with something like 110A. Fuses aren't precise and don't take overcurrent like fuse links do, so you have to err on the high side.

Wait just a cotton-pickin' minute. There's also a page for a 200A alternator and it has a 300A fuse. Not a fuse link. That's 50% more, which would say you should have something like a 150A fuse.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

That's interesting.
I know that many of us are using a 175A fuse with the 130A 3G, and that would suggest ~1.3x the alternator rated capacity.
It would make sense to me the 95A alternator should be fixed right around 125A....
But I'm also sure my 2/0 cables are fine with that kind of current.
What size charging cable do you have with the '96 harness, Cory? 6Ga?

This chart seems to suggest that 6Ga can handle 150A at 4.4 feet long...
https://jascoautomotive.com/automotive-wire-amperage-capacity-chart/

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Yes, it is interesting. And it may suggest that the alternators are capable of kicking out more current than their ratings would imply on a short basis. Perhaps the rating is a continuous rating?

I know my voltage goes up higher than the long-term set point right after starting, but then comes down pretty quickly. So I'm wondering of there is a "map" in the regulator that tries to give the battery a quick hit of power right after starting but then tapers off. And maybe at times that can exceed the rating of the alternator?

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Ryan's old videos used to show the 130A putting out over 160A under load testing.
I don't know how long it could keep that up without the diode board having a meltdown.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

That's what I'm talking about. I doubt it could do it very long as the heat would build up very rapidly, but a fuse has a hair trigger compared to a fuse link, so I'd bet that's why Ford put a 300A fuse on a 200A alternator. And that might be a really good rule of thumb.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

In reply to this post by ArdWrknTrk

My 160 amp on Darth has been there for around 10 years. Only issue was a set of brushes in the regulator. I did switch to a soft start regulator and a larger alternator pulley as the initial load was hard on the polygroove belt (black dust all over the alternator). If it does quit due to diode failure, I have an extra 130 amp 3G left over from my Taurus.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

taskswap

Re: 3G Alternator Conversion with 1996 F150 Harness

In reply to this post by Gary Lewis

Gary Lewis wrote

Yes, it is interesting. And it may suggest that the alternators are capable of kicking out more current than their ratings would imply on a short basis. Perhaps the rating is a continuous rating?

I know my voltage goes up higher than the long-term set point right after starting, but then comes down pretty quickly. So I'm wondering of there is a "map" in the regulator that tries to give the battery a quick hit of power right after starting but then tapers off. And maybe at times that can exceed the rating of the alternator?

I don't know if this helps or distracts, but alternators can also do what's known as a "load dump". I remember from my aviation days that a huge deal was in battery disconnect switches, BlueSea and others sell special versions that have alternator field disconnect terminals. They're designed to break that before breaking the main battery connection because without a battery connected, alternators can go bonkers and put out 100V or more, frying anything still connected. In cars that's rarely an issue because who disconnects their battery while the engine is running? (In small aircraft this is a common checklist step during an emergency landing or fire.)

--
1981 F-250 Custom. 6.6L V8, 4 barrel Holley carb, ARA aftermarket A/C.

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

3G alternators still have the "ground here to test" screw on the brush holder.
This causes the alternator to go full field and you will see 20V or more as it tries to boil your battery. (NOT recommended!)
But it will show if failure to charge is because of the regulator.
This is also why I always suggest looping the y/w "sense" wire straight to the output stud.
If you have it going beyond the fusible link (or Mega-Fuse) like Ford installs it, the alternator is not seeing the system current riseand will quickly overheat.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

In reply to this post by 85lebaront2

Bill - Is Darth's alternator a "160" because it has diodes capable of handling that much current?

I'm asking because I'm wondering how, or even if, the regulators take the output rating of the alternator into account. Looking at Rock Auto's site I don't see a different regulator for the 95A alternator vs the 130A unit, even though a 95A alternator is shown as standard equipment. (The 165A units appear to take an outboard regulator, and I see no regulators for a 200A alternator.) So do the regulators sense the temp of the rectifiers?

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Gary,
Bill's alternator is a RJM modified model.
They had bigger diodes and a thicker copper heatsink.

You must remember that 95A is 'small case' (135mm diameter) and the 130A is 148mm diameter.
The 130A has a bigger heat sink and bigger fans front and rear than the 95A output version.

The different diameter is why I keep saying that if you want a 130A on a V-belt truck you should use the extended pivot (8.25" C-C) version.
While the 95A will allow you enough belt adjustment, the bigger case in combination with the 7" ears just puts it too close to the block and bracket.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Yes, but...

Let me rephrase my question. Bill took a 130A-capable alternator and put "bigger diodes and a thicker copper heatsink" in it so that now it can put out 160A's w/o blowing a diode. But the generating part of the alternator isn't different, so in the same conditions it'll put out the same current it did before.

Which brings me to my question: Does the regulator sense the temp of the heatsink and cut back on the output current to keep from blowing the diodes?

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Bill didn't "take" anything.
He traded someone for a NIB 160A rated alternator that Ryan built over a decade ago.
Back when RJM was a going thing I never had any reason to doubt that their products would live up to their hype.

My understanding is (from the site documentation) that the 160 got better bearings and a better rectifier. (bigger heat sink and higher rated diodes) on an otherwise new Chinese 130A 3G.
But I may be wrong....
I will have to let Bill answer for himself.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

85lebaront2

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

The alternator I bought was from a member on FTE who had bought it from RJM to use. He ran into a situation of needing the money. I bought the alternator, a good sized chunk of wire and end lugs from him for what he paid for it plus shipping. It does not appear to be Chinese as the quality of everything is very good.

I am pretty sure that RJM did exactly what Jim says, replaced the rectifier bridges with higher current ones. These appear to be a 3.8L Taurus/Sable/Mustang etc 130 amp unit right down to the M8X1.25 thread hole in the tensioning lug.

The only issues I have had with it are: Belt slip on startup, one set of brushes/regulator and a front bearing failure. This has been on Darth since probably 2010 or earlier.

Bill AKA "LOBO" Profile

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

I think Ryan used the WAI or Lester number, and this is what made me think the basic chassis was Chinese.

Frankly I haven't had any issues with the electrical components I've got from DB Electrical. It's not like they can't produce quality. They are tasked with making things to a cheap price.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

Ok, I think I understand what's on Darth and where it came from. As well as what failures it has had.

And I assume it would kick out 160A on a continuous basis if called upon. But would the same generator/regulator combo with lessor diodes and heat sink cut back to 130A? The generating portion of the alternator would be the same, so how would the regulator know to cut the current back to save the diodes? Does it sense the temp of the heat sink?

I'm missing something. Maybe I haven't had enough strong coffee today, so I just got a tall Starbucks dark roast and we'll see if there's a dawning in a bit. But if y'all can 'splain it to me...

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

I don't think there's any thermal protection in my stock 130A alternator.
There really shouldn't be any way for a '90-'95 Taurus to pull that much current.

I do have a LRC regulator. But I don't think it has any current limits, just a 14.6V set point.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

85lebaront2

Re: 3G Alternator Conversion with 1996 F150 Harness

Administrator

This post was updated on .

In reply to this post by Gary Lewis

Current is limited by the diode capabilities, voltage output is controlled by the regulator. I do not know if the voltage regulator has any temperature compensation, it may though. Current regulation died with the dynamos.

Ok, it may be a Chinese unit, the sticker is still on it and it says "World Power Systems"

Bill AKA "LOBO" Profile