100 AMP alternator Q&A

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Auzdart

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Anyone know a good place to get a 1 wire 100 amp alternator?
Anyone running one or had any experience good or bad..
Thanks.
 
I'm assuming the reason you want to upgrade your alternator is because you have high electrical loads and probably lights dimming at idle.

If I were you, I would stick with a 3-wire style alternator. I used a delco 12si, made my own bracket, and bought a resistor and diode at radio shack to put in the charging light wire to simulate the light (which is then hooked to keyed power) and hooked the other wire up to the battery + stud on the starter relay (same place as the charge wire goes...I know that doesn't make sense because both the charge output and sense wire are hooked to the same place, but trust me it works better this way).

You also need 10 ga or larger charge wire.

My car has only a 78a 12SI and the volt gauge is rock solid at any rpm and with all items turned on....and its an Advance Auto Parts reman that was $55
 
goldduster318 said:
I'm assuming the reason you want to upgrade your alternator is because you have high electrical loads and probably lights dimming at idle.

If I were you, I would stick with a 3-wire style alternator. I used a delco 12si, made my own bracket, and bought a resistor and diode at radio shack to put in the charging light wire to simulate the light (which is then hooked to keyed power) and hooked the other wire up to the battery + stud on the starter relay (same place as the charge wire goes...I know that doesn't make sense because both the charge output and sense wire are hooked to the same place, but trust me it works better this way).

You also need 10 ga or larger charge wire.

My car has only a 78a 12SI and the volt gauge is rock solid at any rpm and with all items turned on....and its an Advance Auto Parts reman that was $55
Click to expand...

Pictures?
 
goldduster318 said:
I'm assuming the reason you want to upgrade your alternator is because you have high electrical loads and probably lights dimming at idle.

If I were you, I would stick with a 3-wire style alternator. I used a delco 12si, made my own bracket, and bought a resistor and diode at radio shack to put in the charging light wire to simulate the light (which is then hooked to keyed power) and hooked the other wire up to the battery + stud on the starter relay (same place as the charge wire goes...I know that doesn't make sense because both the charge output and sense wire are hooked to the same place, but trust me it works better this way).

You also need 10 ga or larger charge wire.

My car has only a 78a 12SI and the volt gauge is rock solid at any rpm and with all items turned on....and its an Advance Auto Parts reman that was $55
Click to expand...

I've thought about this too. I know bigger always seems to be better, but does anyone REALLY want their undercharged battery charging @ 100 amps? LOL I would think even a 50 amp alternator would be fine.
 
cudavert said:
I've thought about this too. I know bigger always seems to be better, but does anyone REALLY want their undercharged battery charging @ 100 amps? LOL I would think even a 50 amp alternator would be fine.
Click to expand...

That is not how it works, the voltage regulator limits the voltage. The 100A unit has the ability to supply up 100A, but the load dictates the current. A discharged battery has a high internal resistance that limits current.

I would think #6 gauge wire for 100A.
 
KitCarlson said:
That is not how it works, the voltage regulator limits the voltage.
Click to expand...

Well yeah I know that, but let's say your battery is so dead that it can't crank the starter, just fire the plugs. So you push start the car and it fires up. I'd think that it would be pouring a lot of amps into that battery. I don't know if it would take 100 amps, but I have seen low batteries accept 60 amps on a fast charger. Let's just say I'm not a big fan of cooking them up quick.
 
goldduster318 said:
............ I used a delco 12si, made my own bracket, and bought a resistor and diode at radio shack to put in the charging light wire to simulate the light ............................
Click to expand...

You don't need a resistor, all you need is a diode. I used to run one of these not long after they came out. Hook the no2 terminal to "sense" (battery) and no1 is keyed power through a diode. You want the band of the diode like in this internet photo I scammed (photo at bottom of post)

To the OP if you DO upgrade alternator amperage, a couple of things: Do NOT put a great big alternator on the car without changing the poor factory wiring situation. Read this article at MAD electrical

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

and by the way at least part of your problem might be poor headlight wiring, highly recommended to add headlight relays. Crackedback on here is selling a kit

You can easily convert your factory ammeter to a voltmeter, see this thread. Read all three pages, as it covers several different instrument cluster styles

http://www.forabodiesonly.com/mopar/showthread.php?t=119480&highlight=ammeter+conversion

It is also important to understand that bigger amp numbers are not always better. All alternators (if you can find them) have performance curves which show maximum output current versus shaft RPM. There are some 40-45 amp alternators that put out BETTER at low RPM than some of the HIGHER rated alternators!!!

Generally, "more modern" is better. You at least need a Mopar "square back" instead of a "round back" and a lot of guys have had good luck with the modern Denso units.

Earlier, undesirable "roundback" unit at right, newer, desirable "squareback" unit at left. It is IMPORTANT to understand that roundback units came BOTH in pre 70 (grounded brush), in 70/ later (two isolated brushes) and CONVERTED units which were hack jobs by rebuilders, converting older grounded brush units to newer isolated brush. These are often but NOT correctly called "dual field."

mopp_0112_05_z+alternator_and_regulators+replacement_alternator.jpg
 

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67Dart273 said:
You don't need a resistor, all you need is a diode. I used to run one of these not long after they came out. Hook the no2 terminal to "sense" (battery) and no1 is keyed power through a diode. You want the band of the diode like in this internet photo I scammed (photo at bottom of post)
Click to expand...

You can get away without it, but being the crazy person I am, I decided I should also simulate the resistance of the bulb...I don't know if there is any chance the regulator may not last as long without the resistance, but anyway, it doesn't hurt anything.

That picture is wrong. There should be no connector between the "2" terminal and the B+ on the back of the alternator. If you do that, it works just like a 1 wire.

http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Run the remote voltage sensing as I have done and the thing will work absolutely fantastic.

After having a 78a square back mopar alternator and then changing to the 78a 12si Delco, there is no comparison in the performance. The square back still didn't charge well at idle. The 12si is completely unflappable. I believe that a 94a 12si would easily run electric fans, electric fuel pump, MSD, the headlights, blower motor, turn signals, brake lights, radio, charge your cell phone, etc and still keep the volt gauge above 14.
 
goldduster318 said:
...............That picture is wrong. There should be no connector between the "2" terminal and the B+ on the back of the alternator. If you do that, it works just like a 1 wire..
Click to expand...

That statement is true to an extent. "One wire" also means "self exciting" IE there is not switched 12V to the no1 excitation terminal

But if you have a normal front battery, and a direct, LARGE no6 or bigger charge wire and short in length to the battery, the jumpered wire to no 2 will actually work OK for sense.

I DO agree with you, though, I don't normally care for one wire setups or "local" sensing, as the BATTERY is where sensing belongs.

As I eluded to earlier, proper sensing is how I set mine up --long before, by the way, that Al Gore invented the internet

The thing which originally "got me" into using Delcos is that I blew up a couple of Mopar alternators. On my old six-pack 440 car, the original factory pulleys on the crank/ alternator, put the alternator at over 4:1. This means that if the engine is cranking 6K, the alternator is spinning 24000 RPM!!!!! I had a 70 Cuda for a short while, a low budget "run what ya" deal, and ran 5:38s with tall rear tires. That thing went 7K + through the traps.

The mechanical failure mode of the Mopars is, that the cases seem to "work" a little and the vibration can wear notches in the case machined lands where the stator sits. Eventually, this mis-aligns the stator somewhat, and either the rotor slightly ticks the stator, or it begins to vibrate. This mechanically wears the enamel right off the stator windings!!!!

"Back then" I've seen a number of these fail in this manner. If you look at the alternator in darkness, and goose the throttle, it looks like a mini - lightning storm in there. The stator windings arc across to each other.
 
cudavert said:
I would think even a 50 amp alternator would be fine.
Click to expand...

By the time you add together headlights, fans, fuel pump (s), ignition etc 50 amps will not be enough. There is a reason that as vehicles got newer the alt. output went up.
 
I scabbed the alternators, brackets, regulators & wiring out of an '89 GF cop car and a '89 (very rare) 5th Ave. Both were Nippondenso 'mini' units
 
Thanks for all great info. I wanted to run a one wire alternator to clean up the engine bay. The car is not finished yet but I am expecting that I will need a 100 amp alternator because of the load - MSD ignition, electric fuel pump, twin thermo fans and two amps for the stereo.

The Toyota/Denso conversion might be the go for me as I could most probably get one here in Australia, I would just need to get the brackets from Mancini but that's no prob.

Thanks again.
 
Auzdart said:
Thanks for all great info. I wanted to run a one wire alternator to clean up the engine bay. The car is not finished yet but I am expecting that I will need a 100 amp alternator because of the load - MSD ignition, electric fuel pump, twin thermo fans and two amps for the stereo.

The Toyota/Denso conversion might be the go for me as I could most probably get one here in Australia, I would just need to get the brackets from Mancini but that's no prob.

Thanks again.
Click to expand...

Here is a Load Calculator that might help you decide what you need.

http://www.qualitypowerauto.com/pages/AmperageLoadCalculator.php
 
We have a Mopar chrome 100 amp one wire Tuff Stuff. The little built on VR died after a year so I hooked the alt to the factory chrysler VR wires, and it runs great. I still generally dislike its low voltage at idle (700) rpms. Less volt drop at idle than the factory alt, but still a problem. On my next car I will put a denso connected to mopar factory VR.
 
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