 BL: Curious how they "switched the pony coils over to 12 volts". Did they put a bigger dropping resistor on the back of the switch? Originally, the pony coils got their power while the starter was engaged directly from the starter switch using a so-called "by-pass wire". The idea was that the cranking would draw down the voltage to around 5, which is where the coils run when the engine is operating. So, if they kept that by-pass wire in place, you COULD be getting 12 volts straight through to the coils, and since I'm not aware of a 12 volt version of those little pony coils, I'd be a bit concerned. If you have looked that over already, maybe no problem, or maybe they used 12 volt automotive can type coils. On the gauge, there were a couple of reasons it operates the way that it does. One, like John said, the "ignition" switch is off during diesel operation, so that would not work as a source of power. Another fix would have been to run it through an oil pressure normally open switch (like they used for hour meters on A/B/G etc.) so that it would only read while the diesel engine was developing oil pressure. But the real reason as explained to me years back by an old, old, no longer with us Deere dealer service manager, and partner in the old dealership was that in the early days of diesel, people really feared running out of diesel and having to re-bleed the injection system. Also, at 20 gallons of on-board fuel, and wide open fuel consumption on a 720 of no more than 2 3/4 or 3 gal per hour, and a whole lot less on loafing jobs, you could forget just when the last time you fueled up was. So, they made provision for a way to check the fuel level before you went to all the trouble to attempt to crank the diesel if was nearly out of fuel. Whichever is the true answer, it operates so that a momentary press with the engine off powers the gauge from a wire running from the ammeter to the push switch, and then once the generator cut-out switches to closed, it gets its power from the VR cut out circuit. I'll have to think hard about where the negative ground gets you as to the fuel gauge. I'd guess you would have to switch the wires, but by golly I can't say without some research. So, to make the gauge run on the VR but not have it's power supplied from the pressing in of the button, connect the wire that runs from the fuel gauge to the switch, to the black wire that is connected to the switch, but comes from the generator. Typically this black wire would be the closest to the dash panel, which is why it is connected at all times since the switch when relaxed, sits back away from the panel due to spring pressure. I would connect these two with a light jumper and if all is well, then connect them for good. Tape to insulate. You can let the other wire on the rusted button switch if you like, or discard it unitl you replace the switch at a later date, or let one end dangle and tape it off securely. I think that this is the wire that caused the smoke. Here's a bit of a picture...
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