AN EMB120 WAS DISPATCHED WITH A DEFERRED ITEM WHICH DID NOT MEET THE MEL LIST SPECIAL PROCS.

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EMBRAER BRASILIA FLT FROM ZZZ TO XYZ. FIRST FLT OF DAY FOR ACFT AND CREW. I WAS TOLD BY THE FO THAT HE HAD REASON TO BELIEVE A SPECIFIC PROC REQUIRED BY OUR MEL'ED APU BLEED AIR SYS HAD NOT BEEN PERFORMED. THE OPEN DISCREPANCY STATED 'APU DUCT LEAK' ANNUNCIATOR ILLUMINATED. THE MEL REMARKS WERE MAINT REQUIRED ITEMS. A MECH NEEDED TO REMOVE SHUTOFF VALVE AND SAFETY WIRE IT INTO CLOSED POS AND REINSTALL VALVE. THE MECH SIGNED THE ACFT FLT LOG STATING THAT HE COMPLIED WITH MEL. DURING THE FIRST FLT ACCEPTANCE SCAN AS HABIT; THE FO STARTED APU AND BROUGHT APU GENERATOR ON LINE AND ALSO TURNED ON THE APU BLEED TO SEND AIR TO PACKS. AFTER GETTING THE GENERATOR CONNECTED TO THE ELECTRICAL SYS; HE TURNED ON ACFT INTERIOR LIGHTS TO INSPECT COCKPIT AND RELATED PAPERWORK ONLY TO REALIZE THAT WE SHOULDN'T BE USING THE BLEED AIR SYS OF THE APU. BEFORE SHUTTING OFF THE APU BLEED AIR; HE NOTED AIRFLOW BEING SENT THROUGH PACKS -- THIS WOULD NOT BE THE CASE IF THE SHUTOFF VALVE WAS PROPERLY SAFETY WIRED CLOSED. I PHONED MAINT CTL AND INFORMED THEM OF OUR SIT. HE CONTACTED THE A&P THAT SIGNED THE LOG IN A 3-WAY CALL. I ASKED HIM TO EXPLAIN TO ME HOW THIS WAS OCCURRING; HOW COULD WE BE GETTING BLEED AIR INTO PACKS? HE DIDN'T EXPLAIN; BUT INSTEAD TOOK ISSUE WITH THE FLC OPERATING A SYS THAT WAS DEFERRED. HE AGAIN STATED THAT HE PERFORMED THE PROC HIMSELF AND TOLD ME TO TURN TO BLEED SWITCH 'OFF' AND TO FLY THE AIRPLANE. I TOLD HIM THAT I'D GO EVEN FARTHER AND SHUT OFF THE ENTIRE APU AND HAVE ANOTHER MECH IN XYZ INSPECT HIS WORK. WE ARRIVED IN XYZ; CONTACTED A MECH AND HAD HIM INSPECT THE SHUTOFF VALVE TO FIND THAT WE WERE CORRECT; AND THAT THE OTHER A&P HAD LIED AND FALSIFIED THE LOG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS AN EMBRAER 120 AND THE MAINT PROB WAS A RPT OF THE APU DUCT LEAK SENSOR WHICH COULD INDICATE A PNEUMATIC DUCT LEAK FROM THE APU. THE RPTR SAID THE SYS WAS DEFERRED PER THE MEL BUT THE SPECIAL PROCS TO ALLOW THE DEFERRAL WERE NOT ACCOMPLISHED. THE RPTR STATED THE APU BLEED VALVE WAS NEVER MANUALLY CLOSED AND SAFETIED CLOSED TO PREVENT PRESSURIZING A LEAKING APU DUCT. THE RPTR SAID THE MAINT DEPT AND THE MAINT CTL OF THIS AIRLINE IS VERY POOR AND NOT CTLED.