Alternator Confusion, Positive Ground

rasento

New User
My Neighbor has a Farmall M that recently stopped charging the battery. The story goes something like this (I have not been involved until today)

1. At some time in the distant past it was converted to 12v positive ground.
2. Within the last year, he had the Delco alternator rebuilt. He says it worked fine after he reinstalled it.
3. At some time in the past couple weeks, it stopped charging the battery, showing current on the amp meter, and lighting the warning lamp.
4. He replace the ignition switch and the Amp meter. There were sparks as he was hooking things back up.
5. It starts and runs fine if he charges the battery externally.

I looked it over and drew the picture below. There are three wires not connected

1. The output of the excitation switch. He doesn't think he needs it, nor do I.
2. A wire attached to one side of the warning light.
3. The battery lead from the alternator is not attached. I'm not sure where to put it due to the positive ground.

I've never touched the wiring around the alternator on a tractor before.

Any suggestions?

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My Neighbor has a Farmall M that recently stopped charging the battery. The story goes something like this (I have not been involved until today)

1. At some time in the distant past it was converted to 12v positive ground.
2. Within the last year, he had the Delco alternator rebuilt. He says it worked fine after he reinstalled it.
3. At some time in the past couple weeks, it stopped charging the battery, showing current on the amp meter, and lighting the warning lamp.
4. He replace the ignition switch and the Amp meter. There were sparks as he was hooking things back up.
5. It starts and runs fine if he charges the battery externally.

I looked it over and drew the picture below. There are three wires not connected

1. The output of the excitation switch. He doesn't think he needs it, nor do I.
2. A wire attached to one side of the warning light.
3. The battery lead from the alternator is not attached. I'm not sure where to put it due to the positive ground.

I've never touched the wiring around the alternator on a tractor before.

Any suggestions?

View attachment 66997

LFtn4Q4.jpeg
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There, I fixed it.

You MAY have to swap the wires between the two posts on the Ammeter IF it reads backwards.

(Corrected "alternator to Ammeter.)
 
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My Neighbor has a Farmall M that recently stopped charging the battery. The story goes something like this (I have not been involved until today)

1. At some time in the distant past it was converted to 12v positive ground.
2. Within the last year, he had the Delco alternator rebuilt. He says it worked fine after he reinstalled it.
3. At some time in the past couple weeks, it stopped charging the battery, showing current on the amp meter, and lighting the warning lamp.
4. He replace the ignition switch and the Amp meter. There were sparks as he was hooking things back up.
5. It starts and runs fine if he charges the battery externally.

I looked it over and drew the picture below. There are three wires not connected

1. The output of the excitation switch. He doesn't think he needs it, nor do I.
2. A wire attached to one side of the warning light.
3. The battery lead from the alternator is not attached. I'm not sure where to put it due to the positive ground.

I've never touched the wiring around the alternator on a tractor before.

Any suggestions?

View attachment 66997
Alternators are (almost all) negative ground and your battery shows positive ground very rare to find someone convinced they need a positive ground alternator enough to have a special one. This is likely the real problem.

The momentary switch is not needed remove it and wire. The wire from the IGN on key should be connected to the 14 ohm light bulb (which must be good. The batt wire from alternator that is disconnected should be hooked to the ammeter. The ammeter should be changed for negative ground by reversing all the wires from one side to the other. The Batt wire (10 gauge) should go on the ammeter post that is not connected to the solenoid. (if you turn on lights (not running) with the battery and wiring as it is, the ammeter will likely show either + or - if it shows + the ammeter is already switched for negative ground. If it shows - it needs changed along with the battery the other way. If the system still does not work, the alternator may have had the smoke let out from the battery being backwards for an alternator. Jim
 
Hello ra.., welcome to YT! As Jim said “the alternator may have had the smoke let out from the battery being backwards for an alternator.” In YT forum talk that means it was electrically damaged. You will have to quiz them about where they are acquiring their replacement alternator. If it is through regular automotive parts store the alternator will be a NEGATIVE Ground unit. For that woreout’s diagram is correct except the connections of the battery will need to be swapped. The negative post will connect to the chassis and the positive to the starter solenoid.
 
Thanks for all the feedback, especially appreciated for someone who joined today and has not contributed to community yet.

Just to clarify, the positive terminal of the battery is connected to the frame of the tractor.

If I believe my neighbor (he's up there in years, and his recollection of what has been done so far was not helpful), the alternator had been working for years, then he had it rebuilt (at a reputable shop). I would hope they would return it setup the same as they received it. After he installed it, it worked for a while.

I've never messed with positive ground. Based on the replies above, if he is correct that it charged the battery for a while, it must be a positive ground alternator? I'm guessing the only way to be sure would be to take it to the shop and ask?

My neighbor suggested we convert it to negative ground,I was concerned about what direction the starter would turn if we did that.
 
Thanks for all the feedback, especially appreciated for someone who joined today and has not contributed to community yet.

Just to clarify, the positive terminal of the battery is connected to the frame of the tractor.

If I believe my neighbor (he's up there in years, and his recollection of what has been done so far was not helpful), the alternator had been working for years, then he had it rebuilt (at a reputable shop). I would hope they would return it setup the same as they received it. After he installed it, it worked for a while.

I've never messed with positive ground. Based on the replies above, if he is correct that it charged the battery for a while, it must be a positive ground alternator? I'm guessing the only way to be sure would be to take it to the shop and ask?

My neighbor suggested we convert it to negative ground,I was concerned about what direction the starter would turn if we did that.
The starter doesn't care which way the power flows through it. It will still turn the correct rotation. Thousands, maybe millions of these old tractors have been converted from 6 to 12 volts, and mostly from positive to negative ground. Without replacing the starter. Just be careful when you touch that last cable to the battery post. Lots of sparks and smoke means it needs to be wired opposite of what it is. steve
 
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Picture might be worth a lot here. Is it a generator? The drawing doesn’t show a vr but...I’d be interested to see the positive ground alternator just to see one too if that’s the case
 
Picture might be worth a lot here. Is it a generator? The drawing doesn’t show a vr but...I’d be interested to see the positive ground alternator just to see one too if that’s the case
Not really, a pos or neg gnd Delco 10-SI look identical from the outside
 
Thanks for all the feedback, especially appreciated for someone who joined today and has not contributed to community yet.

Just to clarify, the positive terminal of the battery is connected to the frame of the tractor.

If I believe my neighbor (he's up there in years, and his recollection of what has been done so far was not helpful), the alternator had been working for years, then he had it rebuilt (at a reputable shop). I would hope they would return it setup the same as they received it. After he installed it, it worked for a while.

I've never messed with positive ground. Based on the replies above, if he is correct that it charged the battery for a while, it must be a positive ground alternator? I'm guessing the only way to be sure would be to take it to the shop and ask?

My neighbor suggested we convert it to negative ground,I was concerned about what direction the starter would turn if we did that.
I’m thinking you saying he “is up in years” and this “4. He replace the ignition switch and the Amp meter. There were sparks as he was hooking things back up.” Sounds like he thought it was positive ground, which the original 6 volt system was. Reconnected it that way after those replacements, and in Jim’s words “let the smoke out” of his negative ground alternator.
Fixing Farmer said “give us a picture”
JMOR said “Not really, a pos or neg gnd Delco 10-SI look identical from the outside”
That is why I said in reply 7; he better find out where he gets the replacement alternator from that I am fairly certain he is going to need.
 
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Hello ra.., welcome to YT! As Jim said “the alternator may have had the smoke let out from the battery being backwards for an alternator.” In YT forum talk that means it was electrically damaged. You will have to quiz them about where they are acquiring their replacement alternator. If it is through regular automotive parts store the alternator will be a NEGATIVE Ground unit. For that woreout’s diagram is correct except the connections of the battery will need to be swapped. The negative post will connect to the chassis and the positive to the starter solenoid.
''If it is through regular automotive parts store the alternator will be a NEGATIVE Ground unit.''

I don't claim to know what the O.P. is actually dealing with, but most ANY auto parts store with reasonably competent help would be able to source a (+) ground alternator in response to a customer request.

(+) ground alternators are readily available to those who want them and despite what some of you think are NOT as rare as 3-legged unicorns!
 
''If it is through regular automotive parts store the alternator will be a NEGATIVE Ground unit.''

I don't claim to know what the O.P. is actually dealing with, but most ANY auto parts store with reasonably competent help would be able to source a (+) ground alternator in response to a customer request.

(+) ground alternators are readily available to those who want them and despite what some of you think are NOT as rare as 3-legged unicorns!
Bet in all likelihood, probably 5 percent of 6 to 12 volt conversions that were originally positive ground go back with a positive ground alternator. That makes my odds of being correct fairly good. Plus, I am not sure what the “distant past” is but it has only been recently that every Tom, Dick and Harry tractor part wholesaler has offered a positive ground alternator. I guess if what I have posted leads someone to let the smoke out of their alternator, then likely they should not be playing battery cable “Russian roulette” without consulting an on-site expert.
I do appreciate your effort to correct the wiring diagram. Kudos, it does match the information given. Maybe you should not use the words “alternator” and “ammeter” as if they are interchangeable. Now you can go ahead and edit that so no one knows what I am talking about.
 
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My Neighbor has a Farmall M that recently stopped charging the battery. The story goes something like this (I have not been involved until today)
I realize that the tractor is not yours and you don't have a dog in this fight, so to speak. But if the tractor was mine (and it is not, obviously), it would have been money well spent to just convert it to negative ground originally and be done with it. While the positive-ground alternators are available, they are more expensive than a generic that you can get at any parts store and will be a lot less confusing to some shade-tree mechanic who will be called upon to fix it next time. JMO.
 
Nowhere does he say if the tractor has a distributor or a mag. I'm assuming distributor, since his drawing shows a coil. But it does not show which side of the coil is connected to the distributor. That would tell you if it's pos. or neg. ground.
 
Nowhere does he say if the tractor has a distributor or a mag. I'm assuming distributor, since his drawing shows a coil. But it does not show which side of the coil is connected to the distributor. That would tell you if it's pos. or neg. ground.
A coil will work regardless of which way it is wired, so it might or might not be correct for the ground required by the alternator and battery.

As I see it currently:

Right now it is just a guess as to the ground of the alternator and if it is working. The alternator needs to be checked for which ground it is and to see if it is working. (Or just replace it with a known 12-volt Negative ground one and start fresh)

Battery needs to be connected to proper ground to match the alternator.

The alternator needs to be wired properly for the type it is (one or three wire)

The rest of the system needs to be gone through to see that it is correct for the ground being used.
 
Not really, a pos or neg gnd Delco 10-SI look identical from the outside
Yes I understand that’s probably true but my point is what’s he have? And if he does have this it’s relatively uncommon at least special order from somewhere probably not walking into the parts store in town to get one? he also talks about rebuilding it something much more commonly done on a generator although if your positive ground alternator is a level up more expensive wise that might make sense the whole idea of alternator is a little more on the throw away plan 100 dollars or less if you really want to gets you a new one. Few can justify tinkering on it. Generally bearings kept inside the shed and vr actually had about the same lifespan anyway.
My point is let’s see that alternator and the unhooked wire...if it’s a single wire is it one leftover from a vr or is it supposed to go where wore out drew it as part of the conversion harness that got left off?
 

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