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post #1 of (permalink) Old 10-24-2001, 12:53 AM Thread Starter
 
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100 amp or 130 amp alternator ?

Now that the colder weather is here my amp is losing out to the other accesories

I've been surfing around to different Bronco and Ford related sites and 95% say go with the 130 amp alternator conversion. One site claims that the stock 100 amp alternator would be a better upgrade. This guy also claims that the 130 amp unit doesn't provide much more amperage at idle than my stock 65 amp unit. The guy says the 100 amp unit puts out more at idle than the 130 amp unit.

Clearance on my pre-serpentine 86 is not an issue because they sling low under the air pump with no bracket surrounding the alternator, therefore no clearance grinding involved.

What say you ? Which would you go with ?

Malcolm

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post #2 of (permalink) Old 10-24-2001, 04:45 AM
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Re: 100 amp or 130 amp alternator ?

I replaced my alternator with the stock 100. I have the "towing package" and thats what it came with. I don't have any other than stock accessories, so I haven't noticed a loss in power to too many accessories running. My amp gauge has always shown a slight positive charge but I haven't had problems with battery, etc.

post #3 of (permalink) Old 10-24-2001, 08:40 AM
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Re: 100 amp or 130 amp alternator ?

most of the time, those higher output upgrade kits, or lower priced 130 amp alternators are wound so that the faster they spin, they make that higher output, but then at low rpm, they make around the same as stock, maybe a little more, maybe a little less. I personally would reccomend the 100 amp, for that reason, because we dont like the rpm too high in our broncos, otherwise we can say goodbye to any fuel economy.

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post #4 of (permalink) Old 10-24-2001, 08:40 AM
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Re: 100 amp or 130 amp alternator ?

If you spent the vast majority of time AT idle, I'd be more interested in idle performance. ...but who cares what it does at idle? Get the big boy.[img]/wwwthreads_images/icons/smile.gif[/img] I snagged one when I did my EFI swap & have no regrets.


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post #5 of (permalink) Old 10-24-2001, 02:25 PM
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Re: 100 amp or 130 amp alternator ?

Are those 100 and 130 amp units internally (1-wire),
or externally (3-wire) regulated?


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post #6 of (permalink) Old 10-24-2001, 03:01 PM
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Re: 100 amp or 130 amp alternator ?

The 130A is the 3G Mustang alt. It is internally regulated, small case, w/no external fan. If you need to replace the regulator it's virtually impossible w/out removing the alt from the truck.
The 100A large-case Ford alt is externally regulated w/an external fan. The large case will run cooler and the larger bearings tend to last longer. The external regulator is easily replaced on the trail if need be. If you look at any HD truck it'll use a large case alt.
I differ from Steve as idle ouput is very important to me. At least 1/2 of each trailride is spent at idle for me. The other 1/2 rarely sees above 2k, oftemtimes w/the a/c blasting in Moab. If you need to run lots of exterior lights during night 'wheeling, maybe to hook up a strap, stack rocks or to winch idle ouput is paramount.
Every alt will become less effecient as it heats up, this is why serious alt builders rate their alts at "hot" and "cold." I think for truck use (at least the way I use my truck) the large case is the way to go.
If you do a lot of desert running you've got plenty of airflow to help keep the 3G cool. Or w/bogging you've got plenty of RPM's so idle output is not such an issue. Otherwise, I think the 3G is an over-rated alt, not to mention generally more costly - most 3G rebuilds I've seen run at least $130, while the large-case can be had for about $100 (plus about $15 for an external regulator).
There's always other options, GM has a 95amp large case which is supposed to be great, too. Later Broncos w/the tow package did come w 95/100A alts but their side-bolt design makes them hard to retrofit to older motors.
See also: http://soderblom.net/bronco/tech/largealt/

post #7 of (permalink) Old 10-24-2001, 07:27 PM
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Re: 100 amp or 130 amp alternator ? *

OK Shilo; I see your point, but even when you're at idle and stacking rocks or whatever, how much current do you need? Even w/an A/C clutch engaged & the hi-beams & aux lights & a moderate stereo going, you'll still never get above 70A. And when you start winching, it's just toooo easy to bump the gas or shim the throttle - you'd need to do that whether you had a 100A or 130A. And once you start rolling again, you'll be above idle, so again no prob. The difference to me is that with a 100A, you can't get 130A out of it at any RPM. And if you have a good battery with reasonable reserve capacity, instantaneous alternator performance is neglible since even a cheap battery will can put out more - on the order of 6-12 times as much. As long as the alt can recharge the battery when the revs go back up, low idle output is unimportant.

As to the trail fix w/the external regulator: my 130A regulator is mounted to the back of the case with 2 screws - it's the type with the brush holder attached. It's no problem to swap out, but I've never had to. **Also, it's got a single heavy wire from the hot post on the alt to the starter solenoid (battery side) and a light-guage wire to the ALT light in the dash. That's all the wiring for it.**

On the bearing issue - I'd say it's only a concern if you're running your belts too tight. Using good belts and keeping the oil off the pulleys will allow you to minimize belt tension/bearing load.

Mine came from a junkyard and all I did was change the regulator (it was cracked; not burnt out) and I've put at least 100K hard miles on it. Mine is a truck alternator, not a car (Mustang) alternator, so I'm guessing it's not a 3G, but it does have the internal fan. It also uses front-to-back bolts, so it's easily adaptable to non-serpentine trucks. I don't know what year/model/engine it came from since it was on the shelf, but it fits the factory optional holes on the '95 4.9L alternator bracket (the original alt mounted to 2 other holes). I have no idea what it costs new or reman, but junkyards usually sell US truck alternators for $10-50 and I know the regulator w/brushes is $30.


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post #8 of (permalink) Old 10-24-2001, 11:27 PM Thread Starter
 
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Re: 100 amp or 130 amp alternator ?

Thanks guys ! That's a boatload of info to chew on

I guess my problem is that the current Denon amp drains the battery and the stock 65 amp(?) unit will not recharge the battery in a given day's worth of driving. I've gotta charge the battery at night to get an hour's worth of stereo in the mornings. This is only going to get worse when I add an even more powerful second amp.

The battery is 18 months old and in good shape and all the lights, heater fan,etc don't suffer, so it's the alternator in my mind.

Yes I do a bit of idling in city traffic, but admittedly not that much, and it's preceeded and followed by a 20 minute drive into the city at 2000+ rpm, so that ought to charge the battery with the 100 amp or 130 amp unit.

Here in the Great White North, cooling isn't really an issue, except certin Julys and Augusts in certin years. Also I can score a re-manufactured 130 amp 3G alternator for a 95 Mustang for only $190.00 CDN ($127.00 American) while the 100 amp unit is actually more expensive.

From the info presented I'm leaning toward the 130 amp 3G unit as I've faced facts and I guess I don't idle that much. Bearing that in mind I'd think 130 amps ought to recharge a battery faster than 100, right ?

Thanks again guys

Malcolm

p.s./
WD40 The conversion eliminates one of the 3 wire plugs from my stock alt and lets you run a one gauge starter wire from the 1/4" alternator stud(much better set up) through a 150 amp fuse then to the solenoid for distribution.

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post #9 of (permalink) Old 10-25-2001, 07:24 AM
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Re: 100 amp or 130 amp alternator ?

Maybe a pair of yellow top OPTIMAs while your at it too..[img]/wwwthreads_images/icons/wink.gif[/img]

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post #10 of (permalink) Old 10-25-2001, 07:49 AM
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Optimas

Not really worth the money compared to Motorcraft Silver Series or Sears DieHard Gold. Both have 8-year warranties, higher CCA & reserve, & cost 1/2-1/3 what the yellow-top does.


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