John Deere 720 Gas, Conversion from 6 to 12 volt system

Hello Everyone,

Would anyone have experience or a wiring diagram to convert a John Deere 720 gas from 6 volt to 12? Is there any complete kits available? What is the best fitting alternator? If I change the wiring harness, do I use the typical harness offered in adds for the 720 gas or is there something else I should use when completing the conversion. Lastly, can I get 12 volt bulbs to fit or is it best to put a resistor in? Thanks guys!

I’m not a JD guy but know little about them and have a fair knowledge of alternator conversions. I would say the Delco 10si is probably the most commonly used swap alternator for tractors. Is this a pristine restored job that you want the wiring looking stock? If the stock wiring is good enough to keep there is this option. I would have to see a wiring diagram but I believe you could use the heavier wire that fed the Bat. terminal on the regulator to connect to the terminal on the back of the alternator. Due to the fact that your tractor is a positive (+) ground that needs to be changed over the a negative (-) ground to match common alternator polarity. There is only two things needed to do this. On the ammeter in the dash all wires currently on one terminal need swapped to the opposite terminal. Second, you need to connect the wire from the distributor to the negative side of the coil and the coil power wire from the ignition switch possibly running through a resistor needs to feed the plus side of the coil. The only 2 cylinder Deere wiring diagram I have access to is for an “A” it shows the main feed for the ignition and lights as a white wire connecting to the voltage regulator. If this is the case on a 720 that wire will also need placed on the terminal on the back of the alternator. All this is based off you purchasing a internally regulated “one wire” alternator. I actually advise to install a 3 wire alternator, they have an “energize” circuit that enables them to start charging immediately after start up. A one wire alternator often requires to be spun up to a higher rpm to begin charging. The 3 wire alternator actually requires one additional wire to connect to it. The third wire can just loop around to the output. If you are interested in this post back and I can give you details on that connection. Just a helpful hint, a battery that has three water/acid level check caps is a 6 volt battery.
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A John Deere 720 gas has a 12 volt system.. Two 6-volt batterys or one 12 volt.... Generator,, positive ground...
good point, it can have six-volt batteries and be a 12-volt system. In case he is not familiar with the six-volt batteries used for 12 volts: If there is one cable between the two batteries going from positive on one battery to negative on the other, the batteries are hooked in series to make 12 volts. the negative of the first would go to the starter and the positive of the second would go to ground, on a positive ground system.
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Thank you everyone. I'm sorry I’m late. If it’s already 12 volts, this would explain why I could not find any information about a changeover. I inherited this tractor, and while I grew up on 2 old JD B's and an A, I just assumed this would have been six volts too. We did have a JD 2010 and a 3020 diesel which started on 24 volts, so I do know what each battery type is, but still appreciate the help. My uncle, who has passed now, asked me to convert it over to 12 volts because it was not charging. I wonder if he meant, the tractor wasn’t charging, and did not mean he wanted me to convert it. This I will never know. I guess I have a few things to look over and this will make finding the problem easier, at least I hope.

buickanddeere, good to know. Are you saying that the generator is12 volt? It must be. If the generator is bad, (could be the voltage regulator ) I could just get it rebuilt and no need to get an alternator. I'm not fond of the way they stick out of the hood. You’re right, they are ugly.

I'm not currently restoring him. I just want to get him going. I had one of the rims rot badly by the valve stem on the rear tire. I was able to find a use set and tires on Facebook. I have a few things to do.
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Yes I grabbed an operators manual since that's all I could find it would appear that tractor data is incorrect the gas tractor would have been 12 volt not 6. It looks like that occurred with the late g on through the end of the 730 and that 6 volt was actually option for awhile but only on tractors that had lights only and not a starter. And like Jim ME says there should be a cable between battery and battery opposite posts. If any were 6 volt since they had two batteries most likely they were converted long ago. I know the g that is in the shop now the owner mentioned converting so it very well could have been one of those originally without a starter however I would assume that's super rare.
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