There is alot more to take into account when it comes checking an alternator by just referencing the voltage by the battery terminals. All alternators now are controlled by the ecu. If the battery is fully charged there is no need for the alternator to output 14v.
Other aspects must be taken into account before you say an alternator is bad.
Internal wiring ?
Is the diodes functioning properly ?
Is the alternator outputting too much AC ?
Is the alternator receiving a proper signal from the ecu to control its output ?