3G upgrade
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Freshman User
Joined: Mar 2010
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3G upgrade
I got a 1977 f250 with a 390 that i would like to put a 3G alt in.
I have a painless wiring harness just not sure how to wire it in, ive searched on here and know the basics. But the signal wire take it from my anm meter. and my wiring is pretty hacked by somone thanks. and if i rip all the old alt wiring out with regulator will cab still have power.
I have a painless wiring harness just not sure how to wire it in, ive searched on here and know the basics. But the signal wire take it from my anm meter. and my wiring is pretty hacked by somone thanks. and if i rip all the old alt wiring out with regulator will cab still have power.
Junior User
Joined: Nov 2010
Posts: 66
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The way I wired all 3 of my 3g upgrades on my vehicles, 82 gt mustang 351w, 79 f100 302, and 78 f150 300, was I used the factory harness from the late 90's v6 mustang. The battery wire of this harness has fuseable links built in the wire, so I bolted it directly to the starter solenoid. As for the other wires, in plug the original voltage regulator find the red/green wire and cut and hook it up to the red/green wire from the alternator. Same for the yellow wire cut from the regulator plug and hook it up to the yellow wire from the alternator. If you have a capacitor next to the regulator hook it to the yellow wire also. Some people have also just looped the yellow wire directly to the batt positive of the alternator. This works also. All of my vehicles have all the gauges still working just fine.and they are all charging at 14.3v at idle and 14.1v with lights and fan on.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Power into the cab is separate from the charging system.
Post Fiend
Joined: Jan 2006
Posts: 5,037
Likes: 9
From: Kasson, Minnesota
I went with a 1 wire high amp alternator on my 77 to eliminate all the old alternator wiring and just ran a voltmeter gauge and ditched the ammeter. I just use 4 gauge cable and a Megafuse to hook it up. But if you can go to a JY and get an alt and the harness from much cheaper, go that route.
Senior User
Joined: Nov 2011
Posts: 124
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The power wire to the cab does connect to the alt/regulator wiring that is removed when upgrading to the 3G. So yes you do have to reconnect it or there will be no power in the cab. I put an eyelet on it and connected it to the battery side of the solenoid. I know lots of guys put an inline fuse on this. I haven't. When I did mine I read the thread "just did a 3G upgrade" for all the info needed. Page 21 has some good pictures of where that wire is in the factory wiring. It's black with a yellow stripe and is thicker than the rest. Good luck. It's a great upgrade
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