Yamaha EF4500iSE Theory & Diagnostics Manual page 45

Now do the short to ground test on all three of these
coils. Remember, we want to see an open circuit on
a good component.
SUB-COIL SHORT TO GROUND TEST
ExCITER FIELD COIL
SHORT TO GROUND TEST
MAIN COIL SHORT TO GROUND TEST
2-11
Generator Diagnostics
Br R