Table 2-2. Generator Set Troubleshooting (Cont) Malfunction 18. Main generator output voltage  too  low. 19. Main generator output too high. 20. Main generator noisy. 21. Main  generator  frequency fluctuates  or  drifts. 22. Main  generator  fails  to flash. Probable  cause f. Rotating  diodes defective. Exciter-regulator defective. a. Defective bearing. b. Generator  fan — loose or defective. a. Governor system — defective. b. Engine mal- functioning. a. Field   flash circuit  defective. b. Defective exciter   rotor. c. Defective exciter   stator. d. Defective rotating diodes. e. Defective generator  stator. f. Defective — speed   switch. g. Defective excitation assembly. Corrective action f. Check  diodes  (para  9-3).  Re- place  diodes  as  required. (Operator and Organizational Maintenance   Manual). Check exciter regulator (para  8-3).  Replace exciter  voltage  regulator (para 8-10 thru 8-14). a. Replace bearing (para 9-2 and 9-6). b. Inspect  generator  fan. Tighten, repair or replace fan (para 9-2, 9-3 and 9-6). a. Adjust  governor  system  (para 7-2). Repair or replace as required (para 7-3 thru 7-6). b. See items 4, 5, and 6. a. Check field flash relay (K5) (fig.1-11). Disconnect battery negative . Disconnect J9  on  regulator.  Apply  24  Vdc to  terminals  13(+)and  15(-)  on A5 assembly.    Check continuity between terminals 1-14 and 2-15. If circuit is open, replace K5 relay on A5. Check R219 and CR207 in exciter regulator (para 8-3). Replace defective components  as  required  (para 8-10 thru 8-14). b. Check  resistance  of  exciter  rotor. Check for short or ground. Re- place as required. (para 9-2, 9-3,9 -5,9-6 and 9-7). c. Check  resistance  of  exciter stator. Check for short or  ground  (para  9-2). Replace  as  required.  (para  9-2, 9-3,  9-5,  9-6  and  9-7). d. Check rotating diodes (para 9-3). Replace any defective diode (para 9-2 and 9-6). e. Check generator - stator resis- — Check for short or ground para 9-2). Repair or rebuild as required. (para 9-3,9 -4,9-6 and 9-7). f. Check  S9-1,  normally  open,  for proper operation (para 14-19). g. Check R225 and R226 (para 8-12). Change 5 2-15