What was found
(CAN) ON TWO OCCASIONS, THE CREW EXPERIENCED A FIRE INDICATION ON THE APU WHILE THE AIRCRAFT WAS AT CRUISING ALTITUDE. ON BOTH OCCASIONS, THE APU SHUT DOWN AND THROUGH CREW PROCEDURES, THE APU FIRE BOTTLE WAS DISCHARGED. IN BOTH OCCURRENCES, MAINTENANCE INSPECTED THE APU COMPARTMENT AND FOUND NO SIGNS THAT A FIRE HAD OCCURRED AND THE AIRCRAFT CONTINUED IN SERVICE WITH THE APU ON MEL FOR THE DISCHARGED BOTTLE. FOUND PINS ON BLEED VALVE CORRODED, LOAD CONTROL VALVE AND REGULATOR REPLACED.