The diodes are the electronic part of the alternator that convert AC voltage to DC. Switch your multimeter to the lowest AC setting and reattach the test leads to the battery.

In operation, as the alternator’s rotor spins the magnetic poles change from north to south and as a result the current in the stator is constantly reversing direction, which produces ...

Signs of impending alternator failure often include a slight reduction in the voltage reading on the dash, or noticeably duller headlights.