3G alternator conversion Question
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Laughing Gas
Joined: Aug 2010
Posts: 983
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From: Northern Kentucky
3G alternator conversion Question
Preparing to convert from 2G to 3G, but I have several questions regarding fuses.
1.Is there an advantage one way or the other between Megafuses or Circuit breakers?
2. For a 130 amp alternator, what is the minimum and maximum fuse amperage recommended?
1.Is there an advantage one way or the other between Megafuses or Circuit breakers?
2. For a 130 amp alternator, what is the minimum and maximum fuse amperage recommended?
Moderator
Joined: Jan 2001
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From: Virginia
If you are running a single v-belt, you will never see 130 amps. The belt will slip before that happens. It's very common on these single belt swaps to get belt squeal right after a morning start. If that bothers you, I think they do make a special regulator that brings the alternator in slowly to help prevent this. You will still have the low rpm charging advantage the 3g provides.
Only advantage of a circuit breaker is it's renewable, and fuse would be one time. One disadvantage of the circuit breaker, they are more expensive.
Even though you will never see the 130 amp output, I believe I would still put at least a 150 amp mega fuse or circuit breaker in the new line from the alternator to the battery. You can get flat type fuses like the picture below, they are common on GM trucks. You could get the fuse holder from the junkyard(fuse too).
Only advantage of a circuit breaker is it's renewable, and fuse would be one time. One disadvantage of the circuit breaker, they are more expensive.
Even though you will never see the 130 amp output, I believe I would still put at least a 150 amp mega fuse or circuit breaker in the new line from the alternator to the battery. You can get flat type fuses like the picture below, they are common on GM trucks. You could get the fuse holder from the junkyard(fuse too).
Cargo Master
Joined: Oct 2005
Posts: 2,298
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From: NJ
My 130 amps 3g runs out of juice before the belt slips. I forget the exact number but I see about 130 amps out of it with no slippage. IIRC it'll do somewhere around 90 amps at idle though it noticeable drags down the idle of the 6.9. Of course with an old, less grippy, out of adjustment belt, or polished pulleys they can slip well below 130 amp output. I believe it's the 160-200 amp range where duel belts are required.
Lead Driver
Joined: Nov 2013
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A circuit breaker has moving pieces that may eventually stick, considering it would usually just sit there and never move for years and years. A fuse is not going to be affected by age, so I'd go that way myself.
Cargo Master
Joined: Oct 2005
Posts: 2,298
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From: NJ
Regarding circuit breaker vs fuse... I use a 60 amp breaker on the feed to my RTRM box that feeds lighting, blower motor, radio, etc. I use a fuse for the alternator. This was mostly due to space contraints for mounting, but a high amp fuse for the alternator should never pop, it's small enough to keep a spare in the glove box, and it's both simple and reliable. I think I prefer a fuse for that application, though I can't figure there's anything wrong with a breaker if you prefer.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Thanks gentlemen. I think I'll go with a 150 amp megafuse or maybe a 175 if that is more prudent. Now I just need to decide if it is worth the trouble to re-clock the alternator
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Laughing Gas
Joined: Aug 2010
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From: Northern Kentucky
JimsRebel: my current regulator plug has 3 wires. Does that mean that I can just make the white wire loop to the stator and leave the other 2 wires alone?
Sure am glad you guys understand electrical stuff, because it makes my head hurt.
Sure am glad you guys understand electrical stuff, because it makes my head hurt.
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Cargo Master
Joined: Mar 2008
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From: Washington
Are you currently using the stator output for a electric choke cap?
Jim
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Laughing Gas
Joined: Aug 2010
Posts: 983
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From: Northern Kentucky
Not currently using anything to power the choke cap. I wasn't sure how to hook it up on my,shall we say, creative combination of parts. I told you electrical stuff makes my head hurt.
I will soon be installing an Edelbrock 4bbl. that uses 12 volts for the choke. Still have to figure out where to get that 12 volts. Probably just follow Edelbrock's suggestion of Accessory slot in the fuse box.
Another related question, when reclocking a 3G alternator, does it have to be disassembled or can it be loosened and rotated? Utube shows it done both ways. I don't want to mess it up.
I will soon be installing an Edelbrock 4bbl. that uses 12 volts for the choke. Still have to figure out where to get that 12 volts. Probably just follow Edelbrock's suggestion of Accessory slot in the fuse box.
Another related question, when reclocking a 3G alternator, does it have to be disassembled or can it be loosened and rotated? Utube shows it done both ways. I don't want to mess it up.
Post Fiend
Joined: Jun 2003
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From: Black Hills of SD
While not ideal, my "use what you have" way of doing things led me to a large frame 3G on my old hotrod with a pair of 40 amp breakers paralleled. They came from a 4 wheeler sized Superwinch.
That was my first 3G install many years ago and it has worked flawlessly. But then there isn't much demand on the system.
That was my first 3G install many years ago and it has worked flawlessly. But then there isn't much demand on the system.
Moderator
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From: Virginia
Is there a particular reason why you are going to the 3G? If it's just a stock replacement, the stock wires would probably be ok. If you are thinking of adding something like high powered lights, winch, stereo, or something like that, I think I would add a 3rd wire along with the original 2 thick wires on the output, and run the third wire to feed the added equipment through a add-on fuse box mounted somewhere. Ford made the original wiring just big enough for the truck, and of course they messed up on your 2G, the slide on plug for the two wires could not handle the power, melted and caught on fire on a regular basis.
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Laughing Gas
Joined: Aug 2010
Posts: 983
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From: Northern Kentucky
Definitely will add a 4 gauge output wire in addition to the 2 output wires already there. I am adding some lighting, driving lights and additional back-up lights. Mostly making the change to avoid the "flaming alternator syndrome", but better charging at low RPMs can't hurt.
thanks to all for the help.
thanks to all for the help.
Senior User
Joined: Apr 2016
Posts: 291
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From: Austin, TX area
Finally got this swap done. Brought over my mechanic friend as I still don't know what I'm doing with electrical much.
by https://www.flickr.com/photos/93660723@N05/, on Flickr
I do have one question. When I bought the new alt (RockAuto, btw) I also picked up a new belt since the existing one is clearly very old. Existing was a 6PK1255, but the 6PK1285 was the 100amp belt so I thought I should have that one. The belt, however tight I try to set it, still makes a lot of noise. Does the new alt still need to use the old belt size? Evidently the 100a size doesn't seem right.
I do have one question. When I bought the new alt (RockAuto, btw) I also picked up a new belt since the existing one is clearly very old. Existing was a 6PK1255, but the 6PK1285 was the 100amp belt so I thought I should have that one. The belt, however tight I try to set it, still makes a lot of noise. Does the new alt still need to use the old belt size? Evidently the 100a size doesn't seem right.
Post Fiend
Joined: Feb 2008
Posts: 5,831
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From: St Albert, Alberta
Finally got this swap done. Brought over my mechanic friend as I still don't know what I'm doing with electrical much.
3G alternator upgrade 1989 F350 460 gas by TexanAmmo, on Flickr
I do have one question. When I bought the new alt (RockAuto, btw) I also picked up a new belt since the existing one is clearly very old. Existing was a 6PK1255, but the 6PK1285 was the 100amp belt so I thought I should have that one. The belt, however tight I try to set it, still makes a lot of noise. Does the new alt still need to use the old belt size? Evidently the 100a size doesn't seem right.
3G alternator upgrade 1989 F350 460 gas by TexanAmmo, on Flickr
I do have one question. When I bought the new alt (RockAuto, btw) I also picked up a new belt since the existing one is clearly very old. Existing was a 6PK1255, but the 6PK1285 was the 100amp belt so I thought I should have that one. The belt, however tight I try to set it, still makes a lot of noise. Does the new alt still need to use the old belt size? Evidently the 100a size doesn't seem right.
You old belt was 6 rib 1255mm long belt. the new one is a 6 Rib 1285mm long belt.