What was found
"CHECK FIRE DET" WARNING LIGHT AFTER ENGINE START WITH FAULT A AND FAULT B LIGHTS ILLUMINATED FOR ENGINE 1. ENG 1 FIRE DET IND CB (K7) HAS POPPED. CB K7 WILL NOT RESET WITH POWER APPLIED TO A/C. DISCONNECTED CONNECTORS. FOUND CHAFED WIRE W19A.20.4/BLU APP. 1" FROM 2600.J25 BACKSHELL. RE-TERMINATED WIRES AND R&R CONNECTOR AT 2600.J25. RE-INSTALLED CONNECTOR 2600.J25, 2600. P1, AND 9811.P721 AS REQUIRED. PERFORMED OPS CHECKS OF NACELLE AND APU FIRE DETECTION IAW AMM 26.11.00.710.801+23.20.00.710.801. ALL OPS CHECK GOOD. "CHECK FIRE DET", FAULT A/B LIGHTS NO ILLUMINATED. K7 BREAKER NOW REMAINS SET. RETURNED TO SERVICE