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I'm planning on doing an alternator upgrade this weekend on an '81 Bronco and could use alittle more info. I've read all of the threads on the 3G, and Brian Soderbloms site. I've found a local alternator shop that has a 200 amp 3G (powder coated even, extra plus) for $180 , the guy told me that under normal operating rpm ranges and idle that a good alternator would put out more useable amp's than the 3G. He also told me that I probably would never even see the full 200 amp potential out of the 3G, and that I would be alot better off with a 100 amp 1G large case (also in stock $95). I do recall Brians tech article stating something similar about the 3G vs. 1G large case. Is there much truth to this $95 vs $180 is some what of a savings although a powder coated alternator would add a little more bling under the hood. Thanks.
 

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i always used the 3g 94-95 mustang alt. 130 amps and its common to get if you ever fry one you dont have to order one while you veh. is down from a specialty shop. and i never have problems with power.
 

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Thanks for the response. I'm still leaning towards the 3G. I see the good points on both the 1G large case and the 3G, but I was a bit suprised when the guy told me that I wouldnt get the full potential out of the 3G.
 

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FSB warrior
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I dunno I always have around 15 volts with my 130A 3G, I would only have 14 max with my 67 amp, you always want the most amps, especially on a truck

Also thiink of this. You may not see a full 200 amps, but what are you gonna see 160-175????? ok even if you do only see that many, that still beats the 95A by leaps and bounds:rockon
 

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Rest in Peace Friend...
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jonny bravo said:
Thanks for the response. I'm still leaning towards the 3G. I see the good points on both the 1G large case and the 3G, but I was a bit suprised when the guy told me that I wouldnt get the full potential out of the 3G.
I believe Ryan has a graph that shows the output of the various alternators based on the engine RPM.
 

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I say go #G. I have nothing but good to say about the swap. And when they do fail, as someone mentioned, they are easy to find, unlike the older big case alts.
 

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Call Me Ace
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dont forget to upgrade your battery and whatnot...
ace
 

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FSB warrior
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Maybe he ment battery cable??:doh0715:
 

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Ex Navy Nuke
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Sure it does. It's advised to upgrade your charging cable if you go up to the 130 amp. If you go to a 200 amp you're just asking for a fire if you don't upgrage the charge cable. Definitely go 3G
 

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The "charging cable" would be the one from the alt to the relay. That's not a "battery cable". There's no need to change a battery cable because they can already handle over 500A.

And if there's nothing wrong with the alt. cable, I wouldn't even change it. I don't know exactly how much current it's designed to handle, but I bet it's more than ANY alt will produce on that truck. Remember that even a 200A alt will only put out as much current as the battery + the truck's electrical loads are consuming. But if the battery is charged, it'll help with the loads, reducing what the alt puts out. So even with 200A of loads, the alt may only need to produce 100A.
 

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jonny bravo said:
I'm planning on doing an alternator upgrade this weekend on an '81 Bronco and could use alittle more info. I've read all of the threads on the 3G, and Brian Soderbloms site. I've found a local alternator shop that has a 200 amp 3G (powder coated even, extra plus) for $180 , the guy told me that under normal operating rpm ranges and idle that a good alternator would put out more useable amp's than the 3G. He also told me that I probably would never even see the full 200 amp potential out of the 3G, and that I would be alot better off with a 100 amp 1G large case (also in stock $95). I do recall Brians tech article stating something similar about the 3G vs. 1G large case. Is there much truth to this $95 vs $180 is some what of a savings although a powder coated alternator would add a little more bling under the hood. Thanks.
Your supplier is full-of-it

I had my last junkyard Taurus alternator tested and it tested 92 amps at 1000 rpm equivalent and 117 amps at cruising speed of 2000 rpms

Sixlitre
 

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Discussion Starter #18
The cable's and everything I'm replacing new. I'll probably get in touch with Fireguy50 on the harness, the megafuse I'm still debating on. I recall seeing a pic of someone using a circuit breaker instead of a megafuse.
 

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Steve83 said:
The "charging cable" would be the one from the alt to the relay. That's not a "battery cable". There's no need to change a battery cable because they can already handle over 500A.

And if there's nothing wrong with the alt. cable, I wouldn't even change it. I don't know exactly how much current it's designed to handle, but I bet it's more than ANY alt will produce on that truck. Remember that even a 200A alt will only put out as much current as the battery + the truck's electrical loads are consuming. But if the battery is charged, it'll help with the loads, reducing what the alt puts out. So even with 200A of loads, the alt may only need to produce 100A.
How do you figure that a stock battery cable is capable of handling 500A? Most stock cables are no more than 4 guage and everything I have ever read says that 4 guage is only rated to handle 125 amps. Thus, I assumed the reason why all the sites that sell 130 amp and above alternators state that an upgrade of the alternator charging wire to a 2 guage is necessary.

And I will admit I am not an electrical system expert, but I have been told that the battery will only help if the alternator can not handle the load. So you are saying tha regardless of how much headroom your alt has, your battery is always providing amps?

There is no way the stock charging wire that was on my 86's alternator would handle the output on the 3G without heating up and increasing resistance. It was around 10 guage.
 

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Ever put an ammeter on the battery wire to test starter draw? Even a good OEM starter on a small engine pulls ~200A. Get good battery pushing a crappy starter on a big V8 & you can easily see 500A.

The load rating on wire is for a CONTINUOUS load with a high safety factor - cranking & peak-current charging occur very breifly. Consider that Hella rates this switch at only 50A for continuous duty, but 1000A for 10 seconds.

 
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