What was found
AT APPROX FLIGHT LEVEL 1200, LEFT ENGINE FIRELIGHT CAME ON, THROTTLE WAS REDUCED TO IDLE, LIGHT CYCLED ON/OFF. 1ST BOTTLE WAS DISCHARGED AS PER CHECKLIST, LEFT FIRE LIGHT CONTINUED TO CYCLE ON/OFF. 2ND BOTTLE WAS DISCHARGED AS PER CHECKLIST, LIGHT EXTINGUISHED. DID NOT SEE ANY ABNORMAL ENGINE INDICATIONS PRIOR TO ENGINE SHUTDOWN. REPLACED BOTH FORWARD AND AFT FIRE BOTTLES IAW CE560XL M/M CHAP 26-21-01. REMOVED LEFT ENGINE FIRE LOOP, AND INSTALLED NEW LOOP. REMOVED LEFT FIRE DETECTION CONTROL UNIT. ALL DONE IAW CE-560XL MM CHAP 26-11-01 AND CHAP 26-11-02. OPS CHECK SATISFACTORY. RESET ECS BUTTON.