I have a farmall b and trying to finish converting to 12v that someone else started. I have a 10SI (3 wire)alternator. the wire from the batt. Terminal on it runs to a ammeter then it comes off the ammeter to the starter switch (10 guage wire) located on the starter itself, then I have a wire (2 guage i beleive) going from their to the positive battery terminal. Now I also have a 12 guage wire with a diode going from ammeter back to alternator on the #2 terminal to excite it. My problem is I charge the battery and the next day it is dead. I haven't used it in the field yet, still trying to figure this problem out, battery is only year old and holds charge when off the tractor and alternator tested good from autoparts store. Please all comments welcome, this is getting frustrating. I used bobs farmall m wiring diagram, still no luck. Sorry for the long post.
- Thread starter cuttman
- Start date
Janicholson
Well-known Member
IT is wired wrong, but easy to fix.
The wire with the diode needs to connect to the ignition circuit at the ignition switch terminal attached to the coil or ballast resistor.
if it is a Mag neto equipped tractor, the wire needs to be attached to a source of voltage that is on when the tractor is running, and off when it is stopped. An oil pressure switch that is open with no pressure, and closed when under pressure is ideal for this, as it is automatic (NAPA has them).
The wire with diode goes to this new switch ("T"ed into the oil pressure port.) and the switch is supplied with voltage from the starter switch on the hot terminal. A plain SPST toggle switch can be used in place of the oil pressure switch, but it must be turned on manually and off manually each time the tractor is operated.
The other end of the diode wire (whether Mag or Coil ignition) goes to the #1 terminal on the alt, not the #2 as it is now.
The diode must have its band marked end toward the alt.
The #2 terminal on the alt must be hooked to the Bat terminal (short wire).
This should make it work, Get back to us with the results. Jim
The wire with the diode needs to connect to the ignition circuit at the ignition switch terminal attached to the coil or ballast resistor.
if it is a Mag neto equipped tractor, the wire needs to be attached to a source of voltage that is on when the tractor is running, and off when it is stopped. An oil pressure switch that is open with no pressure, and closed when under pressure is ideal for this, as it is automatic (NAPA has them).
The wire with diode goes to this new switch ("T"ed into the oil pressure port.) and the switch is supplied with voltage from the starter switch on the hot terminal. A plain SPST toggle switch can be used in place of the oil pressure switch, but it must be turned on manually and off manually each time the tractor is operated.
The other end of the diode wire (whether Mag or Coil ignition) goes to the #1 terminal on the alt, not the #2 as it is now.
The diode must have its band marked end toward the alt.
The #2 terminal on the alt must be hooked to the Bat terminal (short wire).
This should make it work, Get back to us with the results. Jim
Jim
Thanks for the reply, I just got in from hay field and seen your reply. I looked at the setup again and I have mistakingly said that the wire with the diode was wired to #2 terminal, it's not it goes to #1 like you said. Sooo if I'm thinking right I just need to put an oil pressure switch in the line going from ammeter back to #1 terminal on the alternator, which is the wire that I now have the diode on. Sorry to be so dumb, but after fooling with this so long it makes me feel like I am an idiot!!!! Gregg
Thanks for the reply, I just got in from hay field and seen your reply. I looked at the setup again and I have mistakingly said that the wire with the diode was wired to #2 terminal, it's not it goes to #1 like you said. Sooo if I'm thinking right I just need to put an oil pressure switch in the line going from ammeter back to #1 terminal on the alternator, which is the wire that I now have the diode on. Sorry to be so dumb, but after fooling with this so long it makes me feel like I am an idiot!!!! Gregg
Paul in SC
Member
cuttman,
same thing was happening to one of my tractors, a Super H. Shut it off and go back in day or two and the battery (new) was dead. Tractor was converted to 12 volt neg. ground as per Bob M's diagram. I have other tractors converted with Bob M's diagram and they all work perfect so I knew it was not any problem with that. Had alternator checked by two different auto parts dealers and both said alternator was ok. Posted on this site and got good info from Bob M and Jim Nicholson, which was to replace alternator. What was happening was that when tractor stopped with points closed, a bad diode internally in the alternator was leaking and going to ground via the points, killing the battery. Replaced alternator and no further problem.
same thing was happening to one of my tractors, a Super H. Shut it off and go back in day or two and the battery (new) was dead. Tractor was converted to 12 volt neg. ground as per Bob M's diagram. I have other tractors converted with Bob M's diagram and they all work perfect so I knew it was not any problem with that. Had alternator checked by two different auto parts dealers and both said alternator was ok. Posted on this site and got good info from Bob M and Jim Nicholson, which was to replace alternator. What was happening was that when tractor stopped with points closed, a bad diode internally in the alternator was leaking and going to ground via the points, killing the battery. Replaced alternator and no further problem.
From reading his description, his issue is wiring and not the alternator (Although he could have a bad alternator as well, who knows). If this tractor has the original magneto and he has the #1 terminal wired as he says, directly to the ammeter, then there is nothing to stop the flow of current to the alternator when the tractor is not running. It is draining the battery overnight because voltage is still being applied to the field terminal constantly. By putting either a manual swith to break this connection when the tractor isn't running or an oil pressure switch (as suggested) that will automatically do it for you when the tractor is not running, you will cure this problem.
If you need any more convincing just read this article http://www.chargerr.com/Alternators/ALT.HTM
It's not the greatest article, but it explains it pretty simple.
If you need any more convincing just read this article http://www.chargerr.com/Alternators/ALT.HTM
It's not the greatest article, but it explains it pretty simple.
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