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One wire alternator

F

Fred Werring

Well-known Member
Had a one wire alternator on a 64 Ford 4000, always worked fine.

Put it on an NAA, alternator wont charge. I'm reading battery voltage between the stud and the case, so I know my ground and connections are good.

Revved the motor to max, still won't charge.

Pulled the rubber plug that covered the 2 terminals not used as a 1 wire(battery sense and excite) wired it up like a 3 wire, and it'll charge. (The excite wire i just touched momentarily to the battery stud to get it started charging)

So I guess I've got 2 questions.

Anything I can do to make it work as a 1 wire so I don't have to fool with another wire/diode/light bulb? NAA's had an ammeter instead of a bulb, that's why I wanted to use this alternator.

If not, think it'll be OK to run it hooked up as a 3 wire? Or will I have regulator problems down the road wired like that. When I checked, it looked good, was charging at about 14.5 volts and 10 amps per my clamp on meter.

Fred
 
The internal regulator is the only difference between the one wire and regular alternator. The regular regulator just will not self excite.

The regulator is not hard to replace. You can buy self exciting regulators for around $10.

Type this into Ebay and you will get many hits on ones for sale:

DELCO SELF EXCITED ALTERNATOR VOLTAGE REGULATOR 1 WIRE 10SI 12SI 15SI 27SI 12V
 
I had a Delco that did that, I added a diode from Charlie Uthke, Charlie's Repair, 22195 State Hwy 56, Austin, MN? 55912 [email protected] that fixed the problem. Very economical, installs quick, the ammeter now moves instantly when I start the engine, then the amperage tapers off. Works perfectly.
 
You know those one wire require sufficient RPM to excite!! Maybe the pulley size or RPM is different now from the other tractor and that's the whole problem, hard to see why it worked on one but not another tractor !!!!!!!!!!! Its possible to install a smaller alternator pulley which increases alternator RPM. If you need to convert over to a three wire (which I like better anyway) its soooooooooo easy and it don't matter if you have an ammeter or not.

INSURE ITS TURNING AT ENOUGH RPM ON THIS TRACTOR, there may not be anything else wrong.

John T
 
I picked up some diodes years ago from Radio Shack. I believe there were 4 in the package and it was only a couple bucks. I still have one of them left.
 

As per our electrical Wizard Ol'John T , it's about rpm. A tractor does not approach automotive applications with the same alternator . A "35" amp alternator on a low reving tractor can not even make rated current at full rated tractor rpms .
 
That is one of 2 reasons I use the 3 wire set ups and many 1 wires cannot be easily made into a 3 wire due to how it was done. 2nd reason I used 3 wire is they cost half as much
 
Sounds like this tractor does not spin the alternator as fast as the old one, so not enough rpm to self excite the thing.
You should not have any problem just connecting it as a 3 wire unit, the last box of 1 wire regulators I bought had instructions inside that said if you needed a charge light or wanted it to excite at lower rpm, it's fine to wire it as a 3 wire alt , no problem.
The size (amps) of the one wire alternator determine how much rpm it takes to excite the thing, a 37 amp alternator which is plenty for most classic tractor applications, will excite at half the rpm of a 61 or 72 amp model.
You might also try a smaller pulley or swap out the larger alternator stator for the small 37 amp unit to get it to excite at lower rpm. Many of those tractors came with a 20 amp generator, so a 37 amp alternator is more than up to the job. At the typical auto parts store, you will find little to no difference in price between a 1 wire and 3 wire Delco SI alternator.

I like the 1 wire alternator for many old tractor applications, especially those with magneto ignition, you are replacing a 1 wire generator with a 1 wire alternator and don't need to clutter up the tractor with added wiring and switches.
 
(quoted from post at 09:24:09 10/07/16) Sounds like this tractor does not spin the alternator as fast as the old one, so not enough rpm to self excite the thing.
You should not have any problem just connecting it as a 3 wire unit, the last box of 1 wire regulators I bought had instructions inside that said if you needed a charge light or wanted it to excite at lower rpm, it's fine to wire it as a 3 wire alt , no problem.
The size (amps) of the one wire alternator determine how much rpm it takes to excite the thing, a 37 amp alternator which is plenty for most classic tractor applications, will excite at half the rpm of a 61 or 72 amp model.
You might also try a smaller pulley or swap out the larger alternator stator for the small 37 amp unit to get it to excite at lower rpm. Many of those tractors came with a 20 amp generator, so a 37 amp alternator is more than up to the job. At the typical auto parts store, you will find little to no difference in price between a 1 wire and 3 wire Delco SI alternator.

I like the 1 wire alternator for many old tractor applications, especially those with magneto ignition, you are replacing a 1 wire generator with a 1 wire alternator and don't need to clutter up the tractor with added wiring and switches.
Click to expand...

Adding one wire with inline diode connected to the already there wire from the ignition switch to VR is adding clutter? Glad you told me that!

Rick
 
How many mag ignition tractors have battery voltage available at the ignition switch to supply excite current for the alternator ? NONE, and I am glad to tell you that.
 
(quoted from post at 13:28:34 10/07/16) How many mag ignition tractors have battery voltage available at the ignition switch to supply excite current for the alternator ? NONE, and I am glad to tell you that.
Click to expand...

Hey, I don't know, I only have one tractor with a mag, a Cat D4 7U and that's on the pony motor. And that has a master switch separate from the pony. The pony has a kill switch of it's own.

But it's still one wire and one switch that replaces the wiring to the VR, so still a simpler solution. Not a lot of extra there. And I am glad to tell you that!

Rick
 
Still not near as clean or simple as a properly done 1 wire alternator. And I am glad to tell you that :)
 
(quoted from post at 13:54:01 10/07/16) Still not near as clean or simple as a properly done 1 wire alternator. And I am glad to tell you that :)
Click to expand...

I still prefer the 3 wire. In fact I have a tractor that someone converted to a one wire before I bought it. It's going to get changed over to 3 wire in the spring. Dozer is going to get converted to 12 volt too. That too will be 3 wire. And I'm very glad I told you that :lol: !

Rick
 
Jon Hagen

After further googling I had found the same thing.

I'm gonna go ahead and run another wire to excite the thing and call it good.

Fred
 
It's my FIL's Naa, he wanted to change it to 12v. It has an ammeter.

My 4000 had the battery light, I had installed the 1 wire on it years ago before I learned how easy a 3 wire was, but I lost the use of the battery light. (or so I thought until yesterday)

So my plan was to install the new 3 wire on my 4000 to regain the battery light, and put the 1 wire on the NAA.

Seemed like a plan until the 1 Wire wouldn't charge on the NAA...still unsure why. It'll remain a mystery.

And then after further googling, experimentation, and as was verified by Jon Hagen, found I could just go ahead and run a wire to the excite terminal and call it good. I'll just mount a light under the dash but where my FIL can see it, help remind him if the ignition is left on. Might be a good thing.

But hey, I did manage to run the wire through the ammeter the right direction on the first try.

Thanks guys

Fred
 
Sounds like a good plan. I prefer a gen light (even a hidden one) over a diode because of the unnecessary extra load the diode places on the ignition switch and wiring. A diode will "full field" the alternator, about 3+ amps draw, which almost doubles the load on the ignition switch and wiring, which can cause weak spark and hard starting. A generator light adds less than 1/4 amp load to the ignition circuit, yet is plenty to excite the alternator.
Please use an insulated terminal to connect to the #1 excite terminal,(and / or the #2 sense terminal) as it runs so close to the alternator case that an accidental tug on that wire could short it to the alt case. Buy a GM harness repair plug kit from the auto parts store, buy a plastic insulated terminal or add a bit of shrink tubing to cover a bare spade connector to make it safe.
 
I'm too cheap to buy a gm connector, I just use shrink tube over a female spade.

I ran out of the radio shack indicator lights I like to use, and it's about impossible to buy an incandescent indicator lamp at a car parts store, they're all LED's.

So I paralleled a few 1 amp diodes I had, got things working till I get some lamps. Did notice the 2+ amp current draw, but the tractor starts OK.

It'll all be good eventually, and its not like many of my projects go according to plan anyway

Fred
 
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