TM10-3930-660-20 Table  2-2. Electrical  Troubleshooting  (Cont’d) MALFUNCTION TEST OR INSPECTION CORRECTIVE  ACTION Step 4. Check for defective gauge, defective fuel level sender, or fuel saturated float. Replace gauge and/or fuel level sender if necessary, para. 8-7 and 8-39. LIGHTING  SYSTEM 8. BLACKOUT  LIGHTS DO NOT WORK Check for tripped circuit breaker (CB4), faulty switch, faulty wiring, or faulty circuit breaker (CB4). l The circuit breakers will trip if there is a shorted or grounded wire. l The  circuit  breakers  will  automatically  reset  after  cooling.  They cannot be reset manually. l Under  normal  operating  conditions,  circuit  breakers  should  never require replacement. However, if a circuit breaker does not reset after it has cooled, the circuit breaker is defective and must be replaced, para. 8-12. Check circuit for shorts and bad grounds. Refer to the electrical schematic, page F/O-1. Replace defective electrical components as required, para. 8-12, 8-14, 8-33,  and  8-34. 9. FLOODLIGHTS,  HORN,  AND  BACKUP  ALARM  OPERATE  IN  BLACKOUT  MODE. Check for defective blackout light relay (RY2). Test and, if necessary, replace blackout light relay (RY2), para. 8-24. 10. FLOODLIGHT(s) DO NOT WORK Step 1. Check that floodlight bulbs have not failed. Replace bulbs if necessary, para. 8-32. 2-16