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100 amp 1G swap

Oatmeal

Sr. Member
Joined
May 17, 2009
Messages
664
I recently picked up a 100 amp 1G alternator to swap into my '74 Bronco but, looking at my wiring diagrams, it seems that all of the alternator's output (and all of the vehicles electrical loads, as well) runs through the ammeter on it's way to the battery. I don't think the original wiring is up to the task of handling that kind of current and could cause a meltdown or even a fire if full current were needed. Studying the diagram, I can see no reason why I couldn't run a heavier wire directly from the output post to the battery parallel to the ammeter (thus bypassing it). The ammeter should still function showing vehicle electrical draw but, most likely not charging. However, I have a volt meter also. What do you think, am I flawed in my thinking? Oh, and I really want to use the externally regulated 1G because, it will be the basis for an onboard welder I'll be building. Thanks for any input----------Hans
 
Last edited:

70_Steve

Old Guy
Joined
Dec 13, 2002
Messages
8,317
It should work just fine, capping off the alternator output wire originally connected to the alternator, and running the output of the new alternator directly to the battery, or BAT+ connection on the solenoid. Yes, the ammeter will show a discharge, but what good is that... I connected both ends of that "ammeter loop" together in the engine compartment so I have double the current capacity to the fuse block, not that I'd ever run more out of it than stock.
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,981
Loc.
Memphis, TN, USA, Earth, Milky Way
No, the alternator's output goes primarily to the truck. The battery only pulls what it needs to recharge, which is typically less than 40A. And the voltage regulator only causes the alternator to put out what's needed, and that's RARELY the maximum. So if you're not adding a bunch of key-off loads (like a winch or lights), the stock wire thru the ammeter should be OK.

If you bypass the ammeter the way you described, it'll show virtually nothing (not that it's showing much more NOW). To keep it working (assuming it does now), you have to run a heavier wire thru the little loop on the back of the gauge. But there's really no point - just eliminate the ammeter & install a voltmeter.



A 130A 3G would be a much better choice for an on-board welder. Simply connect the welder to the starter relay along with everything else. The VR will adjust the alternator output for whatever you're doing. If you need to force its output to the max, just add a small switch from F to ground.

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OP
OP
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Oatmeal

Sr. Member
Joined
May 17, 2009
Messages
664
No, the alternator's output goes primarily to the truck. The battery only pulls what it needs to recharge, which is typically less than 40A. And the voltage regulator only causes the alternator to put out what's needed, and that's RARELY the maximum. So if you're not adding a bunch of key-off loads (like a winch or lights), the stock wire thru the ammeter should be OK.

If you bypass the ammeter the way you described, it'll show virtually nothing (not that it's showing much more NOW). To keep it working (assuming it does now), you have to run a heavier wire thru the little loop on the back of the gauge. But there's really no point - just eliminate the ammeter & install a voltmeter.



A 130A 3G would be a much better choice for an on-board welder. Simply connect the welder to the starter relay along with everything else. The VR will adjust the alternator output for whatever you're doing. If you need to force its output to the max, just add a small switch from F to ground.

.
I have a 90 amp GM internally regulated alternator in there now and it is wired directly to the battery (bypassing the ammeter) and the ammeter will still show a discharge just not charging. I want to use an externally regulated alternator so, by just flipping a switch, I can disconnect the vehicles electrical system (through a high amp relay), bypass the regulator and supply full voltage to the field.......pretty much what a Premier Power Welder does. Also, I could always stick a stocker back in there in a pinch. And yes, I do have a winch and off road lights so, alternator draw could exceed wire gauge if the battery fell behind. ----------Hans
 
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