Technical Another alternator thread

After reading most [ all ?] the threads here and elsewhere on wiring, alternators and such, I now have a story/condition to resolve. So @Crazy Steve , come in!
I have been vociferous [ is that the correct word?] on 1 wire , 10si use. OK, now thinking I may come over to the other side. While reading and checking, it does look as if my 1 wire is a 12si, whereas I thought all 1 wires are 10si. Can my alternator be wired up as a 12si or must it be replaced?

Ben

 

12si “one wire” exists.

https://alternatorparts.com/10si-12si-high-output-alternators.html

Don’t know if that’s what you have, or want. I had a one wire on mine, worked fine, until it didn’t, in the middle of nowhere Alabama. Had to replace it in an AutoZone parking lot with a traditional three wire, including wiring change to allow it to work.

I’m not against the one wire alternator as a concept, but I won’t run another one.

 

Not a fan of one wire alternators having had one self destruct electricaly. I just dont see the point of them.

 

Well, not being a fan of one-wires I've never looked closely at the physical differences between them and the three-wire. The difference has to be in the internal regulator, if you could swap that you shouldn't have to replace it.

One-wires can work if installed under the right conditions. One, you don't want any large loads that will be switched in and out of the harness; things like cooling fans, AC, air bag compressors that significantly alter the connected load. A bare-bones harness (basic lights, gauges, ignition) will work the best. Even smaller cumulative loads like a radio, heater, electric wipers can cause issues. Two, and this one is the biggy, make sure the alternator output wire AND the wire(s) feeding your fuse panel are big enough to limit voltage drop to under 3% when using the MAXIMUM available continuous load. This is where the aftermarket harnesses fall down; the furnished wires are too small. To tell the truth, a one-wire can operate the larger loads successfully IF those wires are big enough to limit drop enough, but they'll be much larger than what the kits come with. A three-wire alternator with its 'sense' circuitry will compensate for the upstream drop by increasing output voltage, reducing the need for extra-large wire... but only up to a point. It can't fully correct extreme mis-matches.

 

One wire alternators are made by running an internal jumper from the battery terminal to the sense wire terminal. The reason the OEM doesn't do this is because they want to sense the load near the fuse panel where the greatest chance of voltage drop has occurred. By sensing at the low voltage point it will trigger the alternator to put out more voltage to compensate for it.

The other terminal is the exciter wire that comes from the generator light on the dash. When the alternator is not turning and the key is on the generator light finds a ground through the alternator. When the alternator turns this voltage exites the alternator to charge immediately and puts out voltage to the bulb to turn it off by having 12 volts to both sides.

In a 1 wire alternator you are relying on the spinning of the alternator to create enough of a magnetic field to cause it to start charging. I almost always use a standard alternator with all three wires unless the customer specifically requests a 1 wire as it is a superior way to do it. 1 wire alternators for people who don't understand wiring.

If you don't want to run a generator light on your dash you can substitute a resistor that is comparable to the bulb resistance. The reason for this is so that you don't power the car when you when you turn the ignition off causing run on. Sometimes you also need to add a diode to keep this from happening.

 

I always run a diode with the warning light. The other common mistake is using an LED as a warning light which does not have enough current to prime the system.

 

One wire alternators were originated for farm equipment and tractors that either had Magnito ignition or were/are diesel. That is where I saw them well before the street rodders said "oh look, only one wire to hide on our spotless clean engines rather than three". Remember it was street rodders who didn't extra wires to show who originated it in cars.

As far as changing from or to a one wire 10 or 12 SI alternater all you have to do is swap in the correct regulator. There are a lot of kits on Ebay to turn a 10 or 12 Si alternator into a one wire or you can remove the one wire regulator and replace it with a normal three wire regulator while removing the rubber plug.
The inexpensive way to a one wire alternator eBay item number:384382580341
If you have a one wire and feel that a 3 wire would fit your needs better just go buy a normal three wire regulator from the parts house. The only challenges with working on an alternator are making sure that you mark how the cases are clocked before taking it apart and getting the brushes and springs back in the brush holder and sticking a pin in to hold them in place. With old beat up fingers doing it in the case can be a challenge.
This guy (and I bought one) sells a plug and play anti feedback diode kit that won't please the no wire showing brigade but totally simplifies the put in the diode so the engine will shut off thing. eBay item number:201247906131 .

 

No.

S.I.(system integrated) series of alternators start at '10' and end at '55'. Some are 12V some are 24V and some are both 12/24V units.

10SI are 42 or 63A units, classic looking GM/Ford alternator.
12Si are 78or 94A units, uses disc fan.
17Si are 97A units.

Higher ampacity requires more wire(windings) and a physically larger case.

1W or 3W designation has nothing to do with the alternator make/model/ampacity. It's simply the way the alternator has been wired, or rewired(internally) to function as such.
An internally regulated alternator can, in some way, be rewired to be a 'one wire' unit.

10SI are more common as the aesthetics of that model and ampacity desired(from a one wire conversion) are usually the common demands.

A one wire alternator that is used on anything other than a constant rpm industrial engine is silly.
It's self sabotaging, electrically.

 

Disagree
I understand wiring, but am I supposed to remove my 1 wire alternator that has been there for at least 8 years that I have had my truck and put on a 3 wire because some people say 1 one wire is stupid? I have seen way more modern “smart” alternators for OT cars fail that I have replaced vs my 1 wire. It basically runs the ignition and brake lights and turn signals, headlights work fine but never drive at night so give me good reason to change….

 

I've been moving to the 10DN alternator, which has 3 wires, plus an external voltage regulator. Just because it looks right in a car that might have been built in the 60s.

And they work, so far. If you find an old regulator with the two coils and contact points, you can get that warm fuzzy "non-transistor" feeling when you drive your car. That's worth something, to some of us.

 

Not saying you need to change it...it's your truck. But, with 3 wire you'll have a warning system when the alt fails OR the belt comes off, plus they're easier to get in a smaller town if you don't want to wait, those are the main reasons people use to install a 3 wire or even a 10dn.

 

So can I ask a probably stupid question? The whatever project will have minimal electrical bits, lights, horn, wipers, starter and ignition. I'd like to use one of the mini alternators that Powermaster sells, rated 100 amp max, 70ish amp continuous. They make a drive and mounting kit that puts the alternator on the right side of the engine, mounted off a sbc short water pump. Space considerations are leaning me this way.

Am I crazy?

 

Yeah, you're crazy, but not necessarily because of your alternator choice. If that's all that will fit, it should work fine.

I like to use one that you can find at a parts store if the need arises, but I might drive further from home than you do.

 

Well, there was that time with the nurse, stethoscope, and the instant whipped cream! But I'm much better now...

Seriously, I don't think I'll be driving long distances with the whatever project. And being a "mini" alternator, maybe I should plan ahead and buy 2. The 2nd one for a spare...

 

When the voltmeter drops instantly to 12v or below , that should be warning enough to stop & check things out .
Most towns have someone who works with auto electric , worst case scenario , you could swap regs with a parts store alternator .

 

A 10SI or 12SI can be found almost anywhere, even in small towns if they're large enough to have an auto parts store. Most will come as a 3 wire, but just need to put a jumper form the battery terminal to the excite terminal to self excite them. They of course can also be wired as a 2 or 3 wire by either leaving off the charge light wire for 2 wires, or using it for 3 wire setups.
So it gives you more options than almost any other alternator in a pinch. I have them on two of my cars and wired as two wire setups.

 

Can't you convert a 3 (2) wire unit to one wire by putting on a jumper wire on the plug?

 

Look at my post right above yours!

 

I put a one wire on my avatar roadster and have been driving the snot out of it since 2009, all over the southwest. However, I know that it could fail anywhere at anytime. So, I preplanned for such a failure in a podunk town. If one were to look at my wire harness you would see a wire, untermimated, tucked back, away from the alternator wire, but close by just incase. That wire runs back to my fuse block near the accessory buss. Should I need to install a 3 wire replacement, all I need to do it hook a jumper from the battery post on the 3 wire alternator to the spade terminal in the internal regulator and the folded up wire to the other spade terminal on the internal regulator and the other end to the accessory buss to sense system load. Hopefully, since I planned ahead for such a problem, I won't need it. Just in case, it waits quietly in the loom.

 

S.I. alternators are not 'smart'.
Technology advanced and improved enough that the External Regulator used on 10DN alternators could be reduced down in size and installed into the alternator directly giving birth to the S.I. alternators.
Most 'smart' alternators are simply commanded by the ECU/ECM/PCM on when to turn off for low load and/or mileage reasons. They are built with a couple of added wires which controls the field signal, varying output to very low or turning the alternator off under certain conditions. These can usually be bypassed or ignored leaving only the basic functions to run a 'smart' alternator as a traditional internally regulated alternator.

Ignition. Safety. Liability.

Ignition systems need a constant steady voltage to perform optimally. Voltage drop in the system will kill ignition performance, which affects engine performance.
Power requirements for the ignition system constantly change for the ignition system as your rpms change. Coil needs to be able to saturate and when the points close, give you a nice bluish spark for that sweet combustion power.

Problem with a 1w is it can NOT see('sense') this change in electrical power demands.
1w only monitors its output. It sees(senses) it is putting out 14V at the source(itself), it will just charge at a constant rate and not increase, or decrease, output to match electrical system demands.

Ignition at idle may be fine, increase rpms, more sparks per minute, alternator is not increasing output to maintain a healthy spark. Power drops off.

Even with a healthy battery you are still handicapping yourself.
At best, you are leaving horsepower on the table.
Otherwise your battery is probably not being properly charged and the electrical system is definitively having voltage drop issues.

Safety.
Brake lights are way at the end of the electrical system, our vehicles have small dim lit lights as is, why compound that with excessive voltage drop making those brake lights even dimmer.

Liability.
Just need one itchy trigger fingered moron to lawyer up if they run into you and claim your vehicles brake/taillights were not up to snuff. Maybe not AS deliberate as tinting taillights, which is a no-no, but could open you up to possible negligence.
'It's an old car/truck.' Is not the best of defenses.

10DN's are a fine system and work very well for what they are up to their 61A limit.
10SI will kick the DNs ass up and down the street all day long, but there is something about the clickity-clackity of an external regulator going at it when screwing around underhood

Visceral feelings are a big reason for keeping what was, as-is.
OT 302 Ford still uses the original starter, it's big, it's heavy, and it can be a bitch to get out of the car. When it's cranking away, that 'wah-wa-wa-wah-wa-wa-wah' sound is just, SO. DAMN. GOOD. For the soul.
Couple of my Fuelie 5.0 buds want me to replace it with a late model hi-torque starter.
'It sounds like a WWII fighter plane starting.'
Is that supposed to be an insult? Cuz it's not.

 

If I was worried about leaving horsepower on the table I wouldn’t be running a 235 Chevy. Volts never drop below 13-14 on my gauge.

The law does not require me to bring my vehicle up to 2023 safety standards. Lights are probably brighter that when they were on generator power.

 

It seems some want to over complicate what I consider a very simple system .
The vehicle & its electrical systems will perform as intended with the battery power only for X amount of time , an alternator is basically a way of keeping the battery charged , system does not run of the alternator alone . AFA voltage drops alone , the battery acts as a " damper" or regulator if you prefer . As long as the alternator can maintain the battery , all is good ! Its like water storage , as long as the pump keeps the tank full , everybody's happy .

 

Being electrically challenged, I'd rather put up with a couple extra wires being visable and know that my alternator is capable of supplying whatever demands I place on it and that a replacement is easily available if it fails.
Very basic vehicles or open vehicles often get by fine with small output. But then closed cars with air conditioning and possibly electric fans probably do better with a load sensing alternator when sitting in traffic on a hot day. I always prefer too much capacity to just enough.....

 

Yea . . but that would require me to read.

 

To summarize this thread. 3-wire alternators were designed by factory engineers to run reliably and fairly trouble free with 3 wires. They can and are often converted to 1-wire operation and run fairly well in that arrangement with the understanding that they were not designed to operate in that configuration as reliably. If you run the latter configuration, expect more problems than the former.

 

kind of like any other hot rod part?

 

OKAY!
Question was asked due to reading too much, I guess. Answers were too varied to be helpful, but defiantly appreciated.
From the beginning I ran an 8 GA charging wire from the alternator to the +, downstream terminal on the Amp gauge, thereby bypassing it . An 8 GA to the starter where the battery cable attaches. Over the years, about 13 or so, I had attached a couple , or more, leads directly to the pos battery post. Not good. So I have been "cleaning" them up a bit. As in a Power Terminal Block. Now all power leads can originate from this block. SO, now would have been a good time to go to the two wire. With a sensing wire. I did discover I have a 12si, instead of a 10si. I now know the visual difference, thank you. For what it is worth.
I ended up NOT using a sensing wire. Still a one wire. After all is said and done, with engine at idle, voltages are consistent ACROSS THE BOARD. 14.74 at alternator, dropping all the way to 14. 73 at the battery. And every where measured in between.
Your results may vary.
I will report back after the PNW trip.

Ben

 

It's not always that simple. Let's break these statements down...

'System does not run off the alternator alone'.

Actually, it does run off just the alternator when everything is 'normal'. Under steady-state loads, the charging system produces the full system load plus a bit 'extra' to maintain the battery charge.

'AFA voltage drops alone, the battery acts as a "damper" or regulator if you prefer.'

This is true to a point. The battery will 'handle' instantaneous changes in current demands, reducing the amount of switching events of these high current loads in the charging system and allowing the actual regulator time to decide if it needs to increase/decrease output in reaction. Back when regulators were still user-adjustable, the procedure was to add these large loads while adjusting it to ensure adequate output under all conditions.

'As long as the alternator can maintain the battery, all is good'.

Again, this is true up to a point. Automotive batteries generally have a 12.6 to 12.8 voltage when fully charged. In order to properly charge them, the voltage into them has to be higher than that. How much higher controls the charge rate, and if the output voltage to the battery falls below that due to voltage drop the battery will charge but won't achieve a 'full' charge. As a worst-case scenario, if output voltage drops low enough you'll arrive at your destination and find you have a dead or low battery. If you're using an ammeter to monitor the charging system with an alternator, you'll have little or no warning of this. But in less extreme cases, you may end up with a system that is slow to recharge the battery. If excessive drop reduces voltage to the battery to say 13V, it will charge much slower than if you have 13.5V. In a properly operating system, output voltage of over 14V can be common if the battery charge is low enough or if the load demand is high enough.

In a very 'basic' car like 2OLD2FAST's T bucket and/or cars that are only driven in fair weather and rarely at night, a typical aftermarket harness and one-wire alternator can work just fine. Light loads will prevent excessive drops. But if you need more than that and are adding significant load, voltage drop will rear its head if not addressed and cause issues. I drive my cars at night, and like having a radio and heater as well as wipers. That can easily double or triple the load. The aftermarket harness supplier's 'solution' to this is to sell you expensive 'relay kits', hardly 'simpler'.

 

Sounds sorta like I done. My wiring harness was set up for a three wire setup, I used an older 30 amp one that I had. After I installed electric wipers and AC, I figured I might need to upgrade, so I put on a 65 amp single wire. I tucked the two wire plug out of the way in case I need it again. Since I’m running a GM alternator on a Ford using the Ford bracket, I had to open mount bolt hole up a size for the larger Ford bolt. I carry the old 30 amp unit in the trunk just in case the 65 amp were to quit. Would take less than 15 minutes to swap it back on.

 

I like this article that explains the difference - http://www.madelectrical.com/electricaltech/onewire-threewire.shtml