John Deere 420, 6 to 12 Volt Conversion

What do I need to change on a John Deere 420 to change to a 12 volt system besides the alternator, battery, and coil? Where can I find a diagram for that conversion?
Thanks.
Larry Kastens
 

Change the light bulbs to 12v and switch the coil wires so the hot wire goes to the positive terminal of the coil and the negative terminal goes to the distributor.
 
(quoted from post at 08:48:46 05/14/23)
Change the light bulbs to 12v and switch the coil wires so the hot wire goes to the positive terminal of the coil and the negative terminal goes to the distributor.

Thank you.
larry
 
I am not a JD guy but here is a diagram for an IH. Fairly
sure on those old tractors either brand wires up the
same. Not sure if you are going to use a spending ..one
wire.. alternator or the cheaper common Delco 10si
or Hitachi 3 wire. The diagram shows a Hitachi but the
Delco wires the same. If you have a one wire just
remove the circuits that go to terminals 1 and 2 on the
alternator. See the notes to use a diode option instead of an idiot light, although the light can just be tucked up under the hood and if you think you have a charging problem you can start it up and give it a look to see if it is on or not.
Tractor 6 to 12 volt conversion adding alternator
 
(quoted from post at 13:39:08 05/14/23) I am not a JD guy but here is a diagram for an IH. Fairly
sure on those old tractors either brand wires up the
same. Not sure if you are going to use a spending ..one
wire.. alternator or the cheaper common Delco 10si
or Hitachi 3 wire. The diagram shows a Hitachi but the
Delco wires the same. If you have a one wire just
remove the circuits that go to terminals 1 and 2 on the
alternator. See the notes to use a diode option instead of an idiot light, although the light can just be tucked up under the hood and if you think you have a charging problem you can start it up and give it a look to see if it is on or not.

I am using a one wire Delco alternator. My new coil is 12 volt. Do I need a ballast resistor? Thanks.
Tractor 6 to 12 volt conversion adding alternator
 
(quoted from post at 04:51:00 05/15/23)
(quoted from post at 13:39:08 05/14/23) I am not a JD guy but here is a diagram for an IH. Fairly
sure on those old tractors either brand wires up the
same. Not sure if you are going to use a spending ..one
wire.. alternator or the cheaper common Delco 10si
or Hitachi 3 wire. The diagram shows a Hitachi but the
Delco wires the same. If you have a one wire just
remove the circuits that go to terminals 1 and 2 on the
alternator. See the notes to use a diode option instead of an idiot light, although the light can just be tucked up under the hood and if you think you have a charging problem you can start it up and give it a look to see if it is on or not.

I am using a one wire Delco alternator. My new coil is 12 volt. Do I need a ballast resistor? Thanks.
Tractor 6 to 12 volt conversion adding alternator
/quote]

Sorry about that, No resistor needed with a 12 volt coil. I will have to make a note of mentioning that when I use this diagram in the future.
 
Most alternators require negative ground, if changing from positive to negative ground also reverse ammeter wires if tractor has one.
 
B & D, why for what? You reverse the ammeter wires so charge and discharge are read properly. The system polarity to use a common automotive alternator has to be negative ground. This is due to the diodes used in an alternator. If you connect a common negative ground alternator to a machine that the battery is positive ground the bat. post on the alternator will have a direct short to ground through the diodes.
 
B & D, why for what? You reverse the ammeter wires so charge and discharge are read properly. The system polarity to use a common automotive alternator has to be negative ground. This is due to the diodes used in an alternator. If you connect a common negative ground alternator to a machine that the battery is positive ground the bat. post on the alternator will have a direct short to ground through the diodes.
Why convert to 12V ?
 
B & D, why for what? You reverse the ammeter wires so charge and discharge are read properly. The system polarity to use a common automotive alternator has to be negative ground. This is due to the diodes used in an alternator. If you connect a common negative ground alternator to a machine that the battery is positive ground the bat. post on the alternator will have a direct short to ground through the diodes.
I know all that and teach electrical theory and practical .
The question is why go 12V and hang a butt ugly alternator in a Dubuque two cylinder .
 

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