Slow..Rider,
Double checked in the book, Fat wire is the armature and thin wire is the field.
You can verify that the generator is operating correctly on the bench by motoring it. I used my battery charger with an ammeter in it to test the last one I did.
Jumper the field terminal to the generator frame. Hook the negative battery charger lead to the generator frame. Touch the positive charger lead to the Armature terminal on the generator and it should run as a motor drawing from 4 - 6 amps for a 6 volt generator.
Make sure you've got hold of the generator before you hit it with the positive lead. It jumps pretty good when you hit it with the juice.
This also polarizes the generator in the correct direction.
To polarize on the truck, momentarily connect the BAT terminal on the regulator to the ARM terminal.
