Noisy Generator

Loose or worn generator drive belt.
Loose drive pulley.
Loose mounting bolts.
Worn or dirty bearings.
Defective diodes or stator.
Bent pulley flanges.
Interference between rotor fan and stator leads.
Rotor fan or rotor damaged.
Rectifiers shorted open.
Open, grounded, or shorted rectifier wiring.
Defective regulator.