What was found
EN ROUTE FROM MCI TO PHX THE AIRCRAFT HAD THE FIRE WARNING BELL COME ON WITH OUT ANY WARNING LIGHT INDICATION AS TO WHICH ENGINE OR ANY OTHER INDICATIONS. THE AIRCRAFT LANDED WITHOUT DIFFICULTIES. TESTED THE FIRE DETECTION SYSTEM AS PER BOEING MM CHAPTER 26. CLEANED CONNECTORS AT FIRE DETECTORS AND OPERATING POWER UNITS, CHECKED CIRCUIT BREAKERS AND WIRING FOR THE NR 1, NR 2 AND NR 3 ENGINE FIRE DETECTION SYSTEMS AND NO DEFECTS WERE NOTED. THE AIRCRAFT WAS RETURNED TO SERVICE. (M)