I just completed a 100 amp 1G to 130 amp 3G alternator conversion - the difference is night and day. The 3G was introduced by Ford in 1994 and produces more output at idle than the 1G does at 2,000 RPM. There is minimal dip in my voltmeter when the cooling fans or headlights are switched on, unlike before. 3G alternators are internally regulated and the conversion is easy to do. The physical mounting is pretty much the same too, as the 3" spigot on the mounting ear is the same as the 1G. Easy swap.
3G Alternator Wiring Diagram:
Notes:
- Connect the 'I' wire from 3G alternator to: a) ignition switch if you're running a voltmeter; or b) warning lamp if you're running an idiot light.
- If you're running a warning lamp the alternator will not charge if the lamp burns out. The alternator will charge if you wire a resistor in parallel with the lamp filament.
Worth noting is that many, perhaps most, people replacing installing 3G alternators connect the yellow wire to the alternator output stud (red wire) - after all, it's right there and ultimately connects to the same place. My installation utilized a factory harness, so I connected the yellow wire with one that was an always 'hot' wire that connected to the old external regulator.
Also worth noting is because the 3G alternator has much higher output at low RPM, it's more inclined to give you belt squeal upon startup. I have not had that problem, but I installed a slightly larger, billet aluminum pulley that may have helped prevent belt slippage and squeal. Aluminum is less 'slick' than steel pulleys and better grips the belt, plus the slightly larger pulley: a) turns the alternator a bit slower, thus reducing the load; and b) provides a greater gripping surface for the belt. I'm also using a turnbuckle-type tensioner, allowing me to easily get the belt tension I need - much better than a pry bar and a slotted bracket and bolt!
Keep in mind the 3G doesn't look anything like the 1G, so if 'period correct' appearance is what you're after, you'll need to hunt down someone who produces 3G alternators in 1G cases - they're out there.
Here's one of the many write-ups posted on these upgrades - this one is better than most:
https://www.ford-trucks.com/forums/9...g-upgrade.html BTW, I prefer the wiring diagram posted at the top of this over the one in the intallation thread - it just seems cleaner.
Please note:
- the diagram in the thread shows how to wire the installation if you have a charging lamp (a.k.a. idiot light), while the 1st one does not
- a resistor is NOT required in the switched power source if you don't have an idiot light - or if you're okay with your alternator not charging if/when your idiot light burns out!
- it's highly probable that, if you have an ammeter, it WILL NOT WORK after installing a 3G alternator. This is probably moot, as I suspect most would be running voltmeters in Cobras (they work fine with 3G alternator)