[fuzzfactor]

Much respect for tackling older vintage gear than most :)

>It's usually something stupid.

Like trunk mounted car batteries in ICE cars.

Where the one long copper positive wire reaching up to the engine is longer & thinner than it should be, the short ground wire goes to some sheetmetal in the trunk, and that current eventually makes its way to the starter indirectly through a maze of non-copper pathways through the frame of the vehicle.

Then under ideal conditions the starter never sees more than 11 volts :(

Not even the full 11 volts when the lug in the trunk is painted over before connecting the terminal during assembly :\