Wiring on a Farmall 140 12v Conversion

Got a 140 tractor that was originally 6 volt with a generator where someone converted to 12 volt alternator. Having that it is COLD outside; I thought I would ask here before baring it trying to troubleshoot.

The alternator is not charging and I don't recall if it ever was or not. I have a good alternator that I can put on it, but my question is.....is the wiring correct? Whoever converted it did this to the original wiring and how do you know that it's correct? If not, then the way they wired it could be the suspect. I have attached a wiring diagram that I have from a Farmall 140 Owners Manual....not sure if it is for 6 or 12 volt though.

Thoughts, ideas, suggestions??

Th Alternator that is on it is probably internally remade to be a "one Wire" install. The idea is that if the regulator is made to sense voltage internally all the time (never shuts off) it can start and operate with only the single output wire connected. It does work, but has two issues. one is that the continuous drain of being "on" can and does drain the battery when the unit is not operated for a period ranging from 5 days to a month (some conversions are better than others). The second issue is that they often require higher rotation speed to begin charging. Sometimes needing full throttle to begin charging.
The consensus is that it is a OK method, but oly if the above issues are not a problem.
I recommend that same alternator, or a Hitachi 14231 from a 86 Nissan D21 PU.
They are wired as a three wire installation.
The main output wire, a sensor wire S on the Hitachi, and #2 in a Delco 10SI) and a idiot light circuit. with a source of voltage coming from the ignition switch and having a resistor, or a bulb, or a diode in it to prevent the tractor from running when the switch is shut off. This source is 12gauge, and is hooked to the L terminal on the Hitachi, or #1 on the Delco. Note that the use of the ballast resistor for the coil is required if the coil is original 6v, or labeled with "for use with an external resistor" on the can of the coil. If this solves your issue let us know, or ask more questions. Jim
Bob M diagram

The wiring diagram that you posted is a 6 volt system. The battery only has three cells. I agree with Janicholson, those one wire alternators can a problem at times. I like the Hitachi alternator as it starts charging at low speed.

Thank you both for the input. I've done several conversions from scratch that were the 3-wire GM alternator using Bob M's diagram.

I guess what I am trying to ask is:

Question #1:
How can I hook up a known good Delco Alternator and wire it "3-wire style" using the existing wiring, like the PO did with the "1-wire hookup". OR is it better to take out all the old wiring for the old generator and regulator and start from scratch? It still has the original wiring and the PO used this when he hooked up the alternator.

Question #2:
Can the alternator that is on the tractor be used and hooked up 3-wire style? I noticed someone had put some putty over the #1 and #2 terminals. Is that Alternator internally setup for "1-wire" style or does it depend on how I hook it up? At this point, it could be a good alternator and the wiring be faulty. I do have a couple new 10si alternators though.

i'd dyke that mess out and just rewire with 14awg.

only takes a few feet of wire to wire up charge system, ignition and starting and lamps.

just not that much copper needed on an old farm tractor like that.

I make ALL my own harni'

nothing EVER gained in chopping up one from 1950 nd wondering if it will work or not.

I'm with you SoundGuy, but since the wiring on this tractor is still in good shape and all connections are still there, I figured I would see if there was an easier way (ie. connect green to alternator "bat" and yellow and white to #1 and #2, then leave all other connections unplugged). Also, if someone else wanted to change it back to the original config., the wires would still be there.

*(That is just an example of what info I was looking for). I've got so many projects, I would have liked to nip that one in the bud quickly if I could. If not, I'll just take the time to remove all of the old wires and install new ones.

If you check the internal wiring on a Delco "1 wire", 10SI alternator. Unless you have some strange oddball built many years ago, you will find it has no internal connection to battery voltage, so it will no more discharge the battery than any stock "3 wire" 10SI alternator.

The special "1 wire" regulator is the only different or added part and it excites using residual magnetism in the rotor that generates enough voltage in the stator to excite the regulator and rotor.

Dont believe me ? ,then prove it to yourself. Connect your multimeter's Milliamp section between the battery wire and Bat stud on the alternator to see if a "1 wire" Delco draws any more power than a "3 wire" Delco.

Like I said, unless your testing some 30 year old oddball"1 wire" alternator, you will find the exact same milliamp drain between 1 or 3 wire alternator.

There is no additional internal wiring connecting the "1 wire" regulator to the battery, and nothing is connected to the external #1(excite) or #2 (sense) blade terminals.

The self excite using only residual magnetism, like an old generator does, without any added "tickle" from the battery.

That "1 wire" Delco 10SI alternators discharge the battery, is just another one of those persistant "facts" that aint so, like that ignition coils have an internal resistor.

I have built, rebuilt , modified, installed, retrofitted Delco SI series alternators since they were introduced in the early 70's so I know them well.

The "1 wire" Delco 10 SI needs more rpm to excite than a "3 wire" unit, But many do not realize that a small amp output "1 wire" unit self excites at much less rpm than the big units. In my experience, a 37 amp "1 wire" Delco will excite at 1/2 the rpm of a big 61 or 72 amp "1 wire " alternator. Most folks doing a conversion tend to oversize a "1 wire" alternator, as the big ones are what the stores keep in stock.

Also, If someone already has a "1 wire Delco and is not satisfied with the excite speed, or needs a working alternator light, just wire it as a stock "3 wire" alternator and it will work fine, no need to buy another alternator. The instructions that it is OK to do this came from my "1 wire "regulator supplyer. I have done this several times when all I had on the shelf ready to go was a "1 wire" alternator. Connect the stock regulator plug and all functions as it should.

I have no contest with what you are saying. I also know that many issues have surfaced here on YT related to the one wire systems. Yours (and your supplier) might have the answer, but I still relate to the three wire approach, and recommend it due to the fact that the person doing the conversion just might get the one that does discharge the battery. With respect, Jim

(quoted from post at 06:26:05 01/05/14) If someone already has a "1 wire Delco and is not satisfied with the excite speed, or needs a working alternator light, just wire it as a stock "3 wire" alternator and it will work fine, no need to buy another alternator.

Click to expand...

So, Are you saying that I can do away with the 1-wire setup and wire the existing alternator as a 3-wire and it will work just fine? Given that the alternator is a good one. If not, no big deal because I just bought one from the parts store that is 3-wire.

A one wire is easily changed back to its original configuration by replacing the regulator with a stock regulator. They are cheap on line, and easy to R&R. Putting sense, and lamp circuit wires on it the way it is might work, but also might not, depending on what modifications were made to make it "one Wire". I would wire up the new one (it will work) and replace the VR in the existing Alt. and save it as a reserve, or other application. Jim

Thank you Jim. Yeah, I think I will just take out all the original wiring and put in a new 3-wire alternator. Instead of re-using the old one, I will just keep it for a core. With the "new" ones costing $29.99 at the parts store for one with a 1-year warranty and $34.99 for a lifetime warranty, I think I will just go with those for a hassle free trade off.

Before replacing the alternator and rewiring, try a couple things first.
I am a bit handicapped by not being familiar with the 140 electrical system, but what I see in the wiring diagram, it might be correct for a "1 wire" alternator.( wish your diagram had color codes for all wires At the old regulator location, the Gen, L, and BAT wires should be connected together and taped up neatly.
At the alternator, connect only the old GEN wire to the alt BAT stud as it appears to be in your picture. Seperate and tape up all other wires at the alternator.
Use a 12V test light to make sure you have 12V power at the BAT stud on the alternator.

Make sure the fan and alternator belts are tight so the alternator turns at full speed.

Dig that putty out of the regulator plug hole in the alternator case and with the tractor running half throttle or more, connect a jumper wire from the BAT stud to the left(looking from the rear) #1 regulator blade for a moment. This will "field flash the alternator to start it charging.
If a "1 wire" alternator has lost its residual magnetic field, it will not self excite. Once you field flash it, the residual field will be restored and should not need to be done again unless the battery is disconnected or the tractor is not run for many months.
If this gets it going, just tidy up the wiring and run it. If not, possibly the alternator has a problem and needs to be repaired.

If you decide to go with the new "3 wire" alt, then you need to add wiring to the excite circuit a Janicolson describes.

Here is my schematic for using a Hitachi conversion on a SA. Some object to the use of fuses, your choice. I think this is because the old tractors using a generator didn't fuse the output of the generator so neither should the alternator. But the alternator operates differently than a generator when high current is delivered into a fault. The fuse is lower in value than the rated output of the alternator because on a low RPM engine, the full output is not possible. All modern applications of alternators use a fuse.
Gerry