Alternator wiring and selection (for replacing a generator)

I've been fighting with the miserable generator in my Allis Chalmers D17 long enough. I've done everything to try to keep that generator charging, and enough is enough. It's time to put in an alternator.

I have done a lot of reading up on this, and it seems the hardest part will be to make some brackets to mount it, and adjust it, and make a fan belt fit properly.

However, all this reading has me somewhat confused. First off, I learned to NOT use a ONE WIRE alternator. Not only are they very costly, but wont charge when the engine is running slow or idling. It appears that the only plus about them is that less wiring is needed. But running a few wires dont scare me any.

Anyhow, I already have several old GM alternators with the 3WIRE setup. So, that is what I will use. The alternator type recommended seems to be the 10Si. That is my first puzzle. None of the alternators that I have, have that number on them. But I wonder if that's more of a generic number for the TYPE, not the part number.

I have a GM 3wire alternator right next to me. It has the following numbers on it.
1100794 37A
8C25-12VNEG

I dont know what the first part means, but I assume the 37A means 37 amps. Also the 12V means 12 volts and the NEG means negative ground. (Is this correct?)

But is this then a 10Si?
It looks identical to some photos I have seen on the web for a 10Si.

Ok, so assuming this one will work, there is the THICK RED wire on the screw. Yea, I know that goes to the Battery. Then there is a plug with a blue and a white wire. I know one of these goes to the engine side of the ignition key switch. The other goes right back to the battery terminal and usually is just jumped back to that screw where the battery wire is connected. But which goes where? The white wire has a "R" stamped in the case, and the blue wire has a "F" stamped. (None of the websites mention that). So, which goes where?

Also, I have seen that I need a diode in that wire that goes to the ignition switch. But others say to use a small lightbulb. WHICH IS IT? Or can I use either? (the diode seems easier).
However, if I use a diode, what amperage and voltage diode is required, or for that matter, if I use a lightbulb, what number bulb? (Yea, I am sure its a 12v bulb).

Other than that, I think I am ready to tackle this project, as soon as I get a diode and make sure this is the proper alternator.

Just so you know, this tractor is already 12V and although it came with a POS ground, I already changed it to a NEG ground by reversing the battery cables as well as reversing the wires on the Ammeter and on the Ignition coil.

One last thing. Someone told me I still need to have the alternator modified so it charges at low idle. Yet, others say that is only true on those ONE WIRE alternators.... Which is correct? And if I do need to modify the alternator, what part inside of it needs to be changed?

So many articles on the web, but none seem to get to the fine details or agree on the charging at idle. I do know the pulley on the alternator is a little smaller than the one on the generator. I suppose that can be changed, but wont a slightly smaller pulley make the alternator spin faster? (or do I have that backwards). If the alternator spins a little faster when the engine is at slow idle, I would think that would improve charging.

Thanks

Concerning brackets, I don't know about AC tractors but brackets are available ready to go for many of the old Farmalls, maybe there are some for
AC tractors. I've bought them off of this site. Concerning 1 wire alternators, I think they will charge OK at low RPM's but you have to rev it up
once to get it started charging. I could be wrong. I don't quite understand everything I see here about 1 wire alternators. I have one on my Cub
and it works great. I don't have to have a lot of rpm's to get it to charge. I will add however mine was originally a 3 wire and an alternator
shop converted it to 1 wire so maybe its a bit different. My Cub has a mag so it was easiest to do a 1 wire. I would agree a 3 wire is better for
your application. I have that set up on my H and M and was the best move I ever made.

The 10SI is a single wire. The only trouble I have heard about with single wire is they need some good revs to get charging and they can drain a battery over time. Universal brackets can be bought fairly cheap. Thinking of doing this swap myself.
AaronSEIA

Don't overthink this. Unless you are idling the tractor all day, every day, the alternator will work just fine, even the one wire ones. It doesn't take long for the alternator to return the charge used by the starter and lights. Suppose your starter took 300 amps for 10 seconds. That means that the alternator would need 100 seconds of 30 amp charge to replace it. That's less than 2 minutes of a revved up engine. Yes, your ignition and lights also use some of that charge but they are not the huge draw that the starter takes.

A true 1 wire 10si has a different more expensive regulator in it. They use them in boat applications.
Problem is a true 3 wire 10si will work as a 1 wire if you rev it up enough to get the regulator to leak enough to start the charging process. So people use or make do with a 3 wire in place of a 1 wire.

The 12si 15si and 27si all look different than the 10si. So if yours looks like web pictures and it is only a 37 amp alternator it is most likely a 10si.

R or some time S stands for 'Reference' or voltage sense terminal. This is the one that gets hooked to 12 volts.
It usually goes back to the battery do to live voltage drop but a tractor system is so small you can just hook it to the B terminal on the back of the alternator.

F is field. this is the wire the diode goes in and it needs to be switched where you can turn it on and off. Usually with the starting key.

The system originally came with a dash (idiot light) light bulb. Since most tractors do not have a place in the dash you can use a one way diode. The purpose is to supply 12 volts to the alternator when key is on but not allow 12 volts back into the system with the key off.
To make sure you get the diode facing the right way and in the system properly I usually recommend buying to plug and play system you can find on ebay.
Here is one......

https://www.ebay.com/itm/152043261434?rmvSB=true

A true 1 wire; or a 3 wire; will charge out the gate at a idle.
A 3 wire used as a 1 wire will not charge at idle until it is reved up. Then it will work normally at idle until shut down.

Pretty sure you have a 10DN which was used prior to 10si .10DN requires an external regulator, nothing wrong with that except a little more complex with the wiring.

There is nothing "good" about a 10SI except it is old design, common, and cheap. Many alternator including from GM that are
better design. But they work fine on tractors.

Although also kind of obsolete. a 12SI is better design, same foot print, and same wiring as a 10SI.

If a Delco and the two-prong plug goes into the top, it is a DN and needs an external regulator.
If a Delco that looks similar but the two-prong plug goes in the back - it has an internal regulator and is likely a 10SI
(metal fan), or 12I or 17SI (plastic fans).

One-wire regulator cost me exactly the same as a three-wire regulator. Both charge fine at low idle speeds (1600 alterato
shaft RPM). One-wire tends to kick in at higher RPMs though when you first start the tractor. One it kicks in for the first
time, it works just like a three-wire except it does not sense actual battery voltage like a three-wire.

I have been using Hitachis or Delco CS series alternators on most of my old stuff.

With the three-wire setup - you need to have an "excite" wire that energizes the alternator to make it start to charge.
Usually done by wiring it to the ignition switch. It needs to be isolated from the ignition system though or the alternator
will backfeed and not let you turn off the engine. Using a 5 amp diode is one easy way. If you have an automotive type IGN
switch - just wire the alternator to the ACC terminal and put nothing else there. Then it will isolate the alternator when
the key is off.

If a Delco and the two-prong plug goes into the top, it is a DN and needs an external regulator.
If a Delco that looks similar but the two-prong plug goes in the back - it has an internal regulator and is likely a 10SI

Click to expand...

You've reversed the two, JD!

(quoted from post at 08:27:00 12/17/17) The 10SI is a single wire.

Click to expand...

WHERE in the world did you come up with that statement, Aaron?

10SI alternators, as they left the GM/Delco factory were 3-wire alternators.

Yes, there are aftermarket one-wire abominations assembled in the original-style 10SI cast that are one-wire, but ALL 10SI'3 were originally "3-wire".

Hi

You said:
"But which goes where? The white wire has a "R" stamped in the case, and the blue wire has a "F" stamped. (None of the websites mention that). So, which goes where?"

That concerns me a little bit. The 10SI has a wide plug with both terminals flat (lay your hand flat on a table next to each other) while on the earlier alternators the small plug is more square and the terminals are parallel (hold your hands like you are praying) which is the kind of alternator that uses an external regulator.

The 10SI alternator has a "1" and a "2" where the little plug goes into the side. The "1" is the smaller wire (excite, usually white) and the "2" is the larger wire (sense, usually red). The sense wire goes to the post on the back that goes to the battery, the smaller wire goes to the ignition switch either through a light bulb (plug in style side marker lamp will work, don't recall the number), a resistor (22-27 Ohm, 5 Watt minimum) or a diode. Usually the diode is specified to be 6A at 50V but that may be overkill. I use diodes rated 3A and 1000V because that is what I have on hand and it works for me. The band on the diode goes toward the alternator.

Here is a link to a site showing how to wire the older type regulator which has the <a href="https://alternatorparts.com/gm-external-regulated-alternator-wiring-diagram.html">R and F</a>.
Here is a link to a site with good pictures of the 10SI:
<a href="http://www.madelectrical.com/electricaltech/delcoremy.shtml">Visual Identification and Differences 10SI and 12SI</a>

Hope this helps

The alternator you have is a "10DN", and needs an EXTERNAL regulator.

Original application was a 1968 Camaro, and perhaps some other GM cars of that age.

You WILL NOT see the designations "10DN" or "10SI" marked on any of the units, they are simply series designations.

Having a certain part number chart or reading descriptive information for the part numbers will tell that, or they can be identified by physical appearance.

1N5408 diode is "overkill" for ...'d be willing to drop one in the mail to you.

All the 10 SI ones that I have used have the prongs labeled 1 and 2, and are set at the back of the case. They are
arranged lengthwise side by side, like this - -. The 1 is the excite wire and 2 is the sensing wire. You can get a
plug with the pigtail wires in it ready to go. I have bought one at the farm show that has the diode already installed
in the pigtail wire--very handy. If yours are labeled R and F it may not have the internal regulator like the 10SI.

Here is some pictures.

The 10dn that needs a external regulator





And the 10si that has the internal regulator

I may of told you things backwards. Here is a 10SI with plug on top. 12SI is a better unit and looks the same except has a
plastic fan instead of metal.

An older DN that uses an external regulator also looks the same except the plug is in the back. I have a DN sitting here on my
bench from a 62 Chevy. My Ford 641 tractor also has one on it. Note that for $15, you can buy a fully electronic regulator
for a DN if you want to use it.

In 1962 - the 37 amp Delotron DN was an $8 option. The 47 amp an $11 option. The 52 amp a $32 option.

You can turn a 3 wire 10SI into a one wire with about $10.00 worth of readily available parts an 15 minutes of your time. You do, at least in my experience, need that diode to prevent a slow drain when it's shut down. The ones I've done charge without reving the snot out of them.

I have a DN and an SI on my bench right now. Both big and bulky when compared to more modern alternators. I have had some
tractors where the Delco SI is too big and interferes with the hood closing.

I have several conversions here and both the integral and external regulators. All worked fine right off and have been flawless in service.
Best bet, if buying the old external regulator type is to get both alternator and regulator off the same wrecked car/truck although those are
getting harder to find complete now. I've got that on a 59 IH pickup to replace the generator.
We converted the Cockshutt 50 tractor with a one wire, integral regulator (37 amp) probably 20 years ago. Installed a toggle switch on the
dash to momentarily excite the charging system on startup. Just flick on and off and the ammeter jumps right up there for a few minutes to
recharge the battery. Ammeter never drops below zero even at idle. Making a bracket was simple.

I may be getting a little technical here but will mention anyway. I see posts complaining about, or bragging up one-wire
alternators. They are NOT all the same.

The old cast-iron generators, and the newer aluminum alternators with one-wire work the same way. They both rely on residual
magnetism that is usually present. When it comes to alternators - some have more residual magnetism then others. So some
cut in faster then others. If the alternator has no magnetism at all, the one-wire setup will not work.

The three-wire setup uses an outside power source to create an electro-magnet inside the alternator to get it charging. No
residual magnetism needed.

I pay around $8 for an internal regulator for the SI series - "one wire" or "three wire." NO price difference.

I used a three wire with build in regulater and ligth bulb. I like the light bulb (idiot light). If the light is on you
left the ignition on. If the light is off the alternator is charging. When light is on the light is getting power from
the ignition switch and grounding through alternator. When the alternator starts charging the light has power on both
sides and no ground and therefor the light goes out. The motor has to be speeded up to start charging but then will
charge at a low speed.Works fine for me.

Our local Alt/starter electrical shop here in Alexandria MN charges $50 for a REBUILT 10SI and the diode
kit. New brgs/diodes and checked. Hard to beat that. Pulleys (wide belt) off my Case SC (early 50s)
keyed right on. Not hard to rig a mount.

Yea, that's a 10DN. I use those on my conversions. I also get this type of regulator. (Although cheaper)
Here.

Well just for the record I have 8 tractors with 1 wire alternators get them off ebay for less then $60 they 1)start charging as soon as the tractors fire up 2)Do not run the battery
down when sitting.Here is the list of tractors I have them on.
1)AC D15
2)AC D10
3)Oliver 1550
4)Oliver 1465
5)Oliver 1600
6)David Brown 780
7)Yanmar 330
8)AC 185

What is the pulley ratio? What counts is how fast the alternator spins, not the engine.

If u do go with the gm style alternator, which I have done on a couple tractors,
blow the thing out often. They don't have very good venting fins like say the old
style dodge alternators. They won't last very long otherwise.

You're right and almost any tractor crankshaft pulley is 2X the size of an alternator pulley so it only takes about 700 RPM motor speed to get it charging which is close to idle
on most tractors and no one uses a tractor at idle.Actually I think at even slower speeds the alternator will charge as I've check them and they were charging at a dead idle.

Delco made special brush-screens when the SIs were used on farm-tractors. John Deere used them for awhile until they gave up on Delco alternators (did not hold up very well).

10SI does not blow air as well as the improved 12SI. 10SI is used on many tractors because it is cheap, not superior.
<image src="http://forums.yesterdaystractors.com/photos/mvphoto7742.jpg"/>

Standard Delco pulley when the 10SI was on a car is 2 1/4" OD. Many tractor crank-pulleys are 5-6" OD. If crank pulley is 6", that is a 2.6 to 1 ratio. Engine idles at 700 RPM and alternator is turning at 1800 RPM.

For years I replaced generators and alternators with
10SI alternators. I used to work in a GMC truck
garage and was familiar with the 10 SI. I only got a
few years out of them and have gone through
several of them on the tractors we use frequently.
When I was at the local starter generator shop
trying to get parts for the alternator on the skid
steer. The parts were not in stock. I needed to use
the skid steer and told the shop owner that I was
going to pick a part to get an alternator to put on it.
When I asked what kind to get to my surprise he
said ND. He said he never gets any of them to
repair. I haven?t had any of them go bad so far.

I just had to fix the ND in my Toyota truck. It IS a 1978 however.

When I was a Deere mechanic - John Deere switched from Motorola to Delco SIs for a short period of time on forestry equipment. Very high failure rate. Then Deere went to Denso and I don't recall ever having to fix one.

Chappie, instead of long winded discussions about the pros and cons of which alternator, I RESPECT THE CHOICES YOU ALREADY MADE and will simply try to answer YOUR questions lol BUT NO WARRANTY I don't have any GM data or spec sheets handy I'm going on memory ONLY so it may be right and it may well be wrong SO THERE take it or leave it lol


1) "First off, I learned to NOT use a ONE WIRE alternator. Not only are they very costly, but wont charge when the engine is running slow or idling. It appears that the only plus about them is that less wiring is needed. But running a few wires dont scare me any."

That's your choice and a good one in my opinion


2) Anyhow, I already have several old GM alternators with the 3WIRE setup. So, that is what I will use.

Sounds like a good plan to me

3) None of the alternators that I have, have that number on them. But I wonder if that's more of a generic number for the TYPE, not the part number. I have a GM 3wire alternator right next to me. It has the following numbers on it.
1100794 37A 8C25-12VNEG I dont know what the first part means, but I assume the 37A means 37 amps. Also the 12V means 12 volts and the NEG means negative ground. (Is this correct?)

I THINK SO but no warranty, I have NO GM specs or data to go on

4) But is this then a 10Si?

I THINK SO but no warranty, I have NO GM specs or data to go on


5) Ok, so assuming this one will work, there is the THICK RED wire on the screw. Yea, I know that goes to the Battery. Then there is a plug with a blue and a white wire. I know one of these goes to the engine side of the ignition key switch. The other goes right back to the battery terminal and usually is just jumped back to that screw where the battery wire is connected. But which goes where?

If those 2 small terminals are labeled the "1"/"R" (Excitation) is that which gets 12 volts when the ignition is on, while the one labeled "2"/"F" (Voltage Sense) that can wire to the hot ungrounded battery post or many just jump it to the big main rear output stud on the alternator


6) Also, I have seen that I need a diode in that wire that goes to the ignition switch. But others say to use a small lightbulb. WHICH IS IT? Or can I use either? (the diode seems easier).

YES you can use EITHER of those or even just a Resistor. a) IF you use a lightbulb it needs to be a small marker/indicator INCANDESCENT NOT an LED b) If you use a diode wire it at the correct polarity c) You can use a simple 10 ohm resistor with no worry about polarity and its cheaper then a diode ITS YOUR CHOICE

7) However, if I use a diode, what amperage and voltage diode is required,

As long as its rated for 5 amps (more wont hurt and even less amp rating as the current required for initial excitation is small) and at least 50 Volts PIV it will work.......Its just that a 5 or more amp HAS BIGGER STRONGER LEADS then a wimpy Diode with teeny small wimpy wire leads that break easier

8) or for that matter, if I use a lightbulb, what number bulb? (Yea, I am sure its a 12v bulb).

I don't have that part number, very small marker/indictor INCANDESCENT (NOT LED) seems like its 91 or something I forget

9) I already changed it to a NEG ground by reversing the battery cables as well as reversing the wires on the Ammeter and on the Ignition coil.

YOU DONE GOOD

10) One last thing. Someone told me I still need to have the alternator modified so it charges at low idle.

I NEVER had to do that and don't think its necessary

THERE YOU GO I TRIED TO ANSWER YOUR QUESTIONS BUT IM NOTTTTTTTTTTTT ANY GM EXPERT

John T

if you google the 100794 it comes up as a 10DN Delco Remy with external voltage regulator

Thanks Joe

John T

Like a farmall m and possibly a h

All the replies I’ve seen suggest wiring the 3 wire into the ignition switch.

I’ve got a MF 135 diesel, no ignition switch, Just a momentary starter switch and a manual shutdown. heck, I think the tractor has a total of about 8 wires all together, and that includes two auxiliary wires running to the back installed by the PO to run a weed sprayer.

There is a separate switch for lighting but in the interest of KISS I’d rather not have to remember to turn on the lights to get the alternator going, or have a brain fart and forget to turn off the lights when I park.

Seems a 1 wire would be a simple solution in this case.

Yes? No?

I’ve located a 1 wire 10SI for around fifty bucks on Amazon... seems a reasonable price.

On the 3 tractors I have with alternators (all MM's) instead of running the wire with the diode all the way back to the ignition switch, I just ran it to the + side of the coil. Basically the same thing and took a lot less wire.

How about, instead of a tractor, I would like to put one of these alternators on a '56 International truck. How would I go about hooking THAT up? It has an idiot light already in the dash so I suppose I could use that instead of the diode. But how about the rest of the connections? There is a lot more wiring in a truck than on a tractor, so I would not want to screw this up!

The truck is already 12 volt negative ground.
Since there is no ammeter to connect the large output wire to, what would be the next best place--the ignition switch itself? That's the part which is confusing me. I have not yet begun to track down any of the existing wiring to see what I have. I will be doing that, but I'm thinking it would just be better off to start from scratch.