A B767-200ER RPTS HAVING A CTR DUCT 'OVERHEAT' AND EICAS MESSAGE 'BODY DUCT OVERHEAT.' TECHNICIAN'S PROPOSED FIX WAS TO DEFER AND INOP THE L PACK.

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WITH A MECH IN THE COCKPIT WORKING ANOTHER PROB; NOTED THAT I HAD A CTR BLEED DUCT OVERHEAT LIGHT AND AMBER BODY DUCT OVERHEAT EICAS MESSAGE. THE MECH BEGAN TROUBLESHOOTING THE PROB AND CALLED FOR ADDITIONAL HELP. SOON HAD 4 MECHS IN COCKPIT WORKING THE PROB. THEY DECIDED THAT THEY NEEDED TO PLACARD THE L PACK. THIS INDICATED TO ME A COMPLETE LACK OF UNDERSTANDING OF THE SYS AND AN INCORRECT FIX. THEY REASSURED ME THAT THEY KNEW EXACTLY WHAT THEY WERE DOING. MAINT CTL ISSUED A PLACARD FOR THE L PACK. WHEN THEY RETURNED TO THE COCKPIT WE ENTERED INTO A DISCUSSION OF THE SYS. AFTER ADDITIONAL TROUBLESHOOTING THEY NOW DETERMINED THAT THE PROB WAS NOT THE L PACK; BUT THE APU BLEED AIR; AND THAT THEY NEEDED TO PLACARD THE APU BLEED AIR. I ATTEMPTED TO POINT OUT THIS ONLY SOLVED THE PROB OF BLEED AIR FROM THE APU BUT NOT BLEED FROM THE ENGS TO THE CTR DUCT TO RUN THE ADP. THEY REASSURED ME AGAIN THAT THEY AND MAINT CTL KNEW THE ACFT AND THIS WAS THE PROPER FIX. WE MOVED OUR DISCUSSION TO THE JET BRIDGE. WE WERE NOW DELAYED 40 MINS. I THEN AGREED TO START THE ENGS; SECURE THE APU AND EXERCISE THE FLAPS AND FLT CTLS TO TEST WHETHER THE LIGHT WOULD COME BACK ON. IT DID NOT; AND I AGREED TO ACCEPT THE ACFT. ENRTE TO ZZZ1 I REVIEWED THE QRH; MEL AND OPS MANUAL AND DETERMINED THAT THE FIX WAS WRONG AND UPON ARR AT ZZZ1 CALLED MAINT CTL AND THEY AGREED. THEY SAID THAT THEY WOULD SEND OUT A MECH TO CORRECTLY PLACARD THE APU ISOLATION VALVE AND THE CTR DUCT ISOLATION VALVE. I AM SUBMITTING THIS RPT AT THE SUGGESTION OF MY CHIEF PLT. HE STATED THAT MAINT IS THE FINAL AUTH FOR ACFT AIRWORTHINESS. IN THIS CASE; THEY RELEASED A NON AIRWORTHY ACFT AND I SHOULD HAVE REFUSED IT. I WILL NOT BE BULLIED AGAIN BY MECHS WHO DO NOT KNOW THE ACFT OR ITS SYS.