1 Wire or 3

I have trouble with the one wire. I like using an a switch with accessory to excite the alt. You really only have to run 2 wires. Plug has a red wire that can be tied back into the charge wire on back of alternator. Or you can use a diode ran to anything hot to excite the alternator.
 
NO reason NOT to use a "3 wire" vs. the aftermarket abomination "1 wire" units.

All it takes extra to wire them vs. the "1 wire" units is a diode (1N5408 or similar, less than a buck), or a resistor, or an "idiot light" or a 4-7 PSI N.O. 2 terminal oil pressure switch and a few feet of 16 or 18 GA wire.

Typically a simple rebuilt OEM-style alternator can be had CHEAPER than a "1 wire" unit offsetting the modest extra cost to hook it up.

Ask for an alternator for 1978 Chevy pkup, 350 engine, if 40 or 50 Amps is enough, WITHOUT AC, or if more power is needed spec "WITH AC".
 
I agree with the previous posts. I have put 3 wire alternators on at least 5 tractors in the last few years, with the help of the good folks who post on here. It is really easy to wire them one you take time to understand a little bit about the charging circuit. Its really embarrassing that I was 50 years old before I managed to learn how the alternator is hooked up, but it sure has made a difference in my tractors starting.

ps. You have to understand a little family history here. Growing up, we just always parked the Allis WD on the hill and started it by rolling it down. I guess I just figured once a tractor got old, it had to be started that way. Who knew they could be repaired to start on their own! Dad was a very smart man, but he was not a mechanic.
 
(quoted from post at 18:36:36 12/09/17) My rebuilder suggests 3 wire. Says they can be built to start charging at a lower RPM.
So that is what I use.
our rebuilder is correct. I prefer the configuration with an idiot light on the dash, gives you a heads-up if the belt snaps so you can shut it down before you cook the motor. Even if you forget to look at the temp gauge.
 
Technically, a three-wire hookup does a better job of charging the battery. A one-wire self-exciting alternator has no way of monitoring actual battery voltage. It does not make much of a difference if the battery is not very far from the alternator though.

I prefer the three-wire, but one-wire works well enough. A Delco 10SI (most commonly used on tractors) has to spin at 1600 RPM to start charging with a three-wire hookup. With a one-wire it often has to spin 2000 RPM before it kicks in. No big deal.

Three-wire hookup is easy enough. Excite wire just needs a $1 five-amp diode to power cannot backfeed. Or - if you have an automotive type ignition switch - no diode needed. Just hook the excite wire to the ACC terminal and it gets isolated from IGN when the key is turned "off."

The one-wire setups are not just from the aftermarket. AC Delco also supplied them OEM but not for use on cars or trucks.
 
I have wired up two tractors with a one wire. I used a marine version of the 10si so it starts charging at a low rpm and do not have to rev it up. I got the marine version at my local NAPA auto parts store.
 
GM 1-wire operation:

Most 1-wire alternators have a charging point set around 1200rpm or higher. This is the speed where the internal sensory circuit connects the battery voltage to the regulator, thereby turning the alternator on. Once the voltage regulator turns on, the alternator will remain on and charging until the engine comes to a complete stop. If the engine idle speed and pulley ratio combination does not allow the alternator to come to during start-up, the engine will have to increase the RPM to engage the one wire alternator.
 
I prefer the 3 wire, they are so cheap and so readily available and a piece of cake to wire up.

John T
 

No problem with the 1 wire on my Case 430 backhoe loader tractor. I replaced the 3 wire when it went bad, no downside that I've experienced.
 
Back when I worked rebuilding alt. at a shop we liked the 1 wire ones because most all the customers would screw up hooking them up if they had more than 1 wire to hook up !
 
It depends what your working on, a machine with a magneto usually does not have a factory switch to excite the alternator, so a 1 wire alternator is a clean easy install that adds no clutter or cost. A machine with only a charge light needs the 3 wire alternator to work the charge light and excites at low rpm. A machine with ammeter or voltmeter will work fine with either, the 3 wire gets the nod if the pulley ratio does not spin the alternator overly fast.
 
The alternators I use require 1450 RPM to start charging,I have never run across any crank pulley on a tractor that wasn't 2X as large diameter as the alternator pulley.it only takes
725 RPM for the tractor engine to fire up the alternator.Who in the World operates an old tractor at an idle anyway? No one I know so the RPM thing is just a bunch of BS really.
I don't need an amp meter or light to constantly show if its charging but if a person does they can go on ebay and buy a neat little meter with a magnetic back that will show battery condition and charging rate for about $10 hard wire it into the tractor's electrical system and have a better charge indicator than an amp gauge or an idiot light.
 
Never had a problem with a 1 wire

BUT

Prefer the 3 wire, just cause sometimes I'll shut off the gas and let the tractor run dry, the glowing light on the dash reminds me to turn off the ignition after the engine stops. Not that I get distracted and forget or anything.....melted the coil on a front mount distributor 8n once...

And it does let me know it is, in fact, charging.

Fred
 
According to Delco-Remy - no 10SI ever existed that could start charging until it reached 1600 RPM. Once it starts charging, some can work at low as 1000 RPM. Note I am talking only the 10SI series. I am sure there are a few slight variations, but those are the specs. So you have me wondering what specific alternator are you referring to that cuts in at a lower speed?
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Delco-Remy sold one-wire alternators years ago and likely are all gone. The OEM Delco one-wire regulator was part # 1116409. It is now obsolete from Delco. So anything now if new or newly rebuilt is likely to have an aftermarket regulator. Even then there are variations. A cheap one-wire regulator only rated for a 5 amp field cost $8 new. A HD version for a 7 amp field costs $14 or more. My point is - if people start discussing what is "good" or "bad", some specifics are needed.

The fact remains that no one-wire can monitor battery voltage. It can come close and that is often fine on a farm-tractor that has the alternator and battery close to each other.

As far as high cut-in speed? Kind of meaningless unless the pulley ratios used are mentioned. Delco rates alternators by their own shaft RPMs. Often alterators turn 4-5 times faster then the engine to work.
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3 wire no questions asked. Cost 50% or a 1 wire and will work at all RPM. The 1 wires are not even factory but the Delco 10SI that has been modified to work as 1 wire. Plus the 3 wire I buy at O'Reilly's has a life time warranty if it ever stops working I can take it back and get a new one for free
 
One-wire certainly WAS available from the factory. The self-excite one-wire regulators being used now are likely just clones of the OEM Delco-Remy # 1116409 regulator.
 
One side of the "idiot light" is wired to the coil side of the switch, regardless of whether the light is used to excite the #1 pin on a Delco alternator or simply as a "key on" light.

With a "key on" indicator the other side of the lamp would be grounded and the lamp would glow until switch is turned off or the bulb burns out. Since the light is often used as a charge indicator, the operator would need to be aware that it is now used only as a key on warning and not a no charge warning.

When used to excite the Delco alternator, the other side of lamp grounds through alternator. When engine starts and alternator begins charging, the diode trio in the alternator supplies 12 volts to alternator side of the lamp and it goes out indicating the charging circuit is working. Hence, in this case the lamp can serve both as a "key on" and a no charge indicator.
 
I don't know if Delco-Remy makes any parts for the old 10SI alternators anymore. So I guess it is fair to say that any modern repair now with aftermarket parts is a "bastardization." Certainly is no price difference between one-wire and three-wire regulators. I pay the same for either and I figure they all come from China now.

Delco 100 series were all three-wire and called "light duty."
Delco series 102, 110, and 116 were fire-resistant, dust-resistant, or heavy-duty and available with a one-wire hook-up.
 
I'm using the 62 amp delco alternators off ebay about a dozen sellers sell.I put a meter on them to check the charging out when I put them on and everyone has started charging as soon as as I
crank up the tractor and will keep charging no matter the RPM. 62 amps is way over kill on most any old tractor BTW 15 amps would be just fine for most old tractors especially diesel unless a lot
of lights were used a whole lot. Many people seem to miss the fact that the alternator is usually running over 2X the RPM of the tractor because of the larger crankshaft pulley.
 
Alternator specs go by the shaft RPM of the alternator, not the RPM of the engine. Most auto engines run the alternator 4-5 times faster then the engine so they can charge at low engine RPMs.
 
I've been saying the specs are for the RPM of the alternators but the alternators do not need to turn 4 or 5 times as fast as the spec required just as fast as required will still make them charge
at a somewhat lower rate but it works fine for an old tractor that has very little current draw compared to a car or truck.
 
The way I do it I get the best of both....a "key on" reminder when the engine is not running, and a light to let me know the alternator is charging.

Nothing wrong with a 1 wire, I've used them, just decided I prefer the 3 wire with an idiot light for the reasons I gave.

Fred
 

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