TM 10-3930-653-14&P 4-7-2-2. Alternator and regulator Condition Probable cause Corrective action No output Sticking brushes Free, replace brush and brush spring. Dirty brushes and slip rings Clean brushes and slip rings Loose connections or broken leads Tighten or solder connection Replace leads Open stator winding. Repair or replace stator Open rotor winding. Replace rotor Open diodes Replace diodes Shorted rotor Replace rotor Shorted stator Repair or replace stator Grounded "BAT" terminal Replace insulator Broken fan belt. Replace belt Excessive output Broken neutral point wire (color of wire Replace wire is white). Faulty voltage regulator Check regulator operation Poor grounding of alternator and voltage Tighten terminal connection regulator "E" terminal Broken ground wire (color of wire is Replace wire black). Low output Loose or worn fan belt Tighten or replace belt Sticking brushes Free; replace brushes and spring it necessary Low brush spring tension Replace brush spring Faulty voltage regulator Check regulator operation Dirty slip rings Clean slip ring Partial short, ground, or open in stator Replace stator winding. Partial short or ground of rotor winding Replace rotor Open diode or faulty diode Replace diode Noisy alternator Loose mounting Tighten mounting bolts Loose drive pulley Tighten pulley Faulty ball bearings Replace bearing. Improperly seated brushes Seat brushes properly. 4-90