John Deere 720lp generator to alternator

Timmy87

New User
I AM HAVING PROBLEMS WITH MY 720. It started running bad trying to die, someone told me it could be the coil getting hot so I decided to go ahead and switch it from a positive ground generator to a negative ground alternator since the generator wasn't charging anyways. I put a new coil on it, mounted the self excite alternator, took the voltage regulator off since my alt had a internal reg, changed it from ammeter to volt meter and hooked it up negative ground. Now it wont run, it will start but dies right after startup and volt meter does not work. Im sure its a simple wiring issue just not sure what.
 
Change out the resistor behind the dash on the left side, when tractor starts up and if you hold some pressure on starter and if tractor keep running that tell you that resistor is bad. Easy fix. .. (Also reverse wires on coil if not done already.)
 
You can't change an ammeter for voltmeter quite so easy as this for that. Ammeter is pass thru on charging connection to battery which is also supply for the entire tractor. Voltmeter is wired differently with no pass thru function at all.

If you didn't know this like the back of your hand then this is entire problem. Why did you change the ammeter for a voltmeter as the ammeter would still work fine with alternator, voltage does not matter to an ammeter. You can have both meters but if your concern is only one hole to fit it in, then my suggestion would be to revert back to ammeter, you may have to swap wires around on it from one terminal to the other when changing grounding system from positive to negative like you did.
 
You didn?t need to change the coil?-only to reverse the
polarity.

And it is probably running from the resistor bypass built into
the starter solenoid. You missed a connection somewhere. I
would just put a larger ammeter in it instead of a voltmeter.
 
The coil I put on it has a internal resistor so I crossed over that one and it still dies as soon as I let off the starter button. I have switched the wires on the coil so many times I dont remember how it is suppose to go lol. Could it be something from me switching it to negative ground that I didnt get rewired Also the reason I changed the coil is the original one was full of water or something. I also tried putting original coil on to see if that fixed it. But no luck.
 
For starters, that tractor came with a 6 volt coil, the resistor is there to knock the 12 volts from the tractor down to 7 volts or so for running without burning the points. There is a wire coming from the starter that bypasses the resistor to give the coil more voltage for starting the engine. This is the preferred system to use. You now have a 12 volt coil that does not need the resistor, however, that coil won't give you quite as much spark during starting. It sounds to me like You have the 12 volt coil hooked to the wire that comes from the starter solenoid and bypasses the resistor instead of the wire that comes from the ignition switch for running. If you choose to keep the 12 volt coil that does not need a resistor you need to take the two wires that go to the resistor, disconnect them from the resistor and connect them together somehow. I forget if the resistor uses spade connectors or ring connectors, probably spade, anyway connect the two directly together. Only that wire should now go to the coil, the bypass wire from the starter is not needed.
 

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