What was found
ENGINE FIRE NR 2 LIGHT W/AUDIO CAME ON/OFF SEVERAL TIMES IN FLIGHT. CREW CONFIRMED NO ACTUAL FIRE AND THEN TURNED BACK TO LAND A ORIGINATING BASE. LIGHT EXTINGUISHED ON IT'S OWN, CAME BACK ON DURING DOWNWIND APPROACH AND FINAL. EXTINGUISHED AGAIN AND STAYED OFF DURING LANDING AND TAXI TO RAMP. MAINTENANCE INSPECTED NR 2 FIRE/FLAME DETECTORS IAW MM 26-11-210-001. CLEANED LENS & PERFORMED FIRE DETECTION TEST WITH OVERHEAD TEST SWITCH. COULD NOT DUPLICATE, SYSTEM CHECKS GOOD. ACFT RETURNED TO SERVICE.