The alternator on my 1993 Maxima suddenly caused a buzzing noise on the radio and the output was measured 12.3 volt.. I removed the regulator unit on the side and made electrical measurements but found no fault. However I dismanteled the complete unit and inspected it for obvious faults, it was found that one end of a winding was never soldered and was only pinched between the hook wires. The wire was bent away from the hook and both cleaned and well soldered and the unit assembled. Its operation is now back to specification. The buzzing noise can also be developed if one diode is open circuit. Regards Marten du Preez, Pretoria, South Africa.