AIRWORTHINESS DIRECTIVE WORK NOT ACCOMPLISHED CORRECTLY ON B737-400.

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IN SUM: REF AIRWORTHINESS DIRECTIVE: WHILE WORKING AIRWORTHINESS XX-VV-ZZ ON ACFT ABC; I MISINTERPRETED A PORTION OF THE AIRWORTHINESS DIRECTIVE WHICH ADDRESSED THE WIRE ROUTING AND SPLICING OF THE FIRE BOTTLE CIRCUIT. AFTER OBSERVING SEVERAL ACFT BEING DONE IN THIS MANNER ACFT ZZZ WIRING WAS ROUTED AND WIRED NOT TO THE AIRWORTHINESS DIRECTIVE SPECS. WE THOUGHT THE REASON FOR THE CHANGE BEING THE ELIMINATION OF CUTTING AND SPLICING SOME WIRES. SAFETY WAS NOT COMPROMISED. ALL SUBSEQUENT CHKS AND TESTS WERE GOOD. AFTER 3 ACFT WERE WIRED IN THIS CONFIGN IT WAS DETERMINED THE LETTER OF THE AIRWORTHINESS DIRECTIVE WAS BEING VIOLATED. I CONTACTED MY MAINT FOREMAN AND ADVISED HIM OF THE SIT. THE FOREMAN WAS ASKED TO REQUEST ENGINEERING TO REVISE THE PORTION OF THE AIRWORTHINESS DIRECTIVE DEALING WITH THE WIRING. THIS WOULD ELIMINATE WIRE SPLICES AND GND WIRE REPLACEMENT. HE AGREED TO DO SO AND CONTACTED ENGINEERING AT XYZ AND PRESENTED THE PROB. UPON RETURNING HE INFORMED US THAT THE ENGINEER THOUGHT WHAT WE WERE DOING WAS A GREAT IDEA AND SAW NOTHING WRONG WITH WHAT WE WERE DOING. WE WERE NOT ADVISED IF THE WIRING PORTION OF THE AIRWORTHINESS DIRECTIVE WOULD BE REVISED. THE FOREMAN'S INSTRUCTIONS WERE TO DO THINGS AS WE HAVE BEEN DOING; THAT IS NOT WIRING THE ACFT TO THE AIRWORTHINESS DIRECTIVE SPEC. ANOTHER 2 ACFT WERE MODIFIED IN THIS MANNER. UPON DISCUSSION WITH OTHER SHIFT MECHS WE REALIZED THAT WHILE THE INTENT OF THE AIRWORTHINESS DIRECTIVE HAD NOT BEEN VIOLATED; THE LETTER AND SPECS WERE IN VIOLATION. THE LEAD MECH CONTACTED THE ENGINEER PREVIOUSLY CONTACTED BY THE FOREMAN AND WAS ADVISED UNDER NO CIRCUMSTANCES COULD WE DEVIATE FROM THE AIRWORTHINESS DIRECTIVE SPECS. THE ENGINEER ALSO RELATED THAT THE FOREMAN WAS ADVISED OF THIS DIRECTIVE. WHEN CONFRONTED WITH THIS FACT THE FOREMAN THOUGHT IT WAS NO BIG DEAL BUT AGREED TO HELP RECTIFY THE SIT. HE WAS GIVEN THE TAIL NUMBERS OF THE AIRPLANES INVOLVED SO A PLAN COULD BE DEVISED FOR CORRECTING THE WIRING. BEFORE THE AIRWORTHINESS DIRECTIVE NOTE EXPIRED WE TALKED WITH A DIRECTOR OF MAINT AND A MEMBER OF ENGINEERING IN XYZ. IT WAS AGREED TO BRING THE AFFECTED AIRPLANES IN THAT WKEND FOR CORRECTION BEFORE THE AIRWORTHINESS DIRECTIVE EXPIRED. WE WERE ADVISED THAT WORKING THE WKEND MAY BE REQUIRED. THE WKEND PASSED AND WE WERE AGAIN ADVISED THAT THINGS HAD BEEN TAKEN CARE OF OR RESOLVED. THIS WAS JAN/MON/96. ON JUL/MON/96; 6 MONTHS LATER; WE WERE SENT OUT TO PERFORM THIS AIRWORTHINESS DIRECTIVE COMPLIANCE ON ACFT ZZZ. THIS SHOULD HAVE BEEN DONE IN JAN/96. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR WAS ASSIGNED TO WORK THE WIRING PORTION OF AIRWORTHINESS DIRECTIVE XX-VV-ZZ ON ACFT ABC; A B737-400; FIRE EXTINGUISHER CIRCUIT REWIRING. RPTR MISINTERPRETED THE JOB CARD INSTRUCTIONS ON WIRING SPLICES AND ROUTING OF THE WIRE BUNDLES. THE COMPLETED WORK WAS NOT AS SPECIFIED IN THE AIRWORTHINESS DIRECTIVE JOB CARD. IT WAS THE MECHS' OPINION THE WIRING JOB THEY HAD DONE WAS A BETTER INSTALLATION AND AVOIDED CUTTING WIRE BUNDLES AND ADDING SPLICES. THE MECHS DOING THE WORK REQUESTED THE MAINT FOREMAN TO CONTACT THE ENGINEER WHO WROTE THE JOB CARD TO ALLOW SOME DEV FROM THE AIRWORTHINESS DIRECTIVE SPECS. THE FOREMAN ADVISED THE RPTR AND MECHS INVOLVED THAT THE ENGINEER HAD BEEN CONTACTED AND IT WAS APPROVED TO DO THE JOB THEIR WAY. THIS LATER PROVED WRONG. THE ENGINEER WOULD ALLOW NO DEV FROM THE JOB CARD SPECS. THIS AIRPLANE WAS EVENTUALLY REWIRED 6 MONTHS AFTER THE AIRWORTHINESS DIRECTIVE EXPIRED. NO EXPLANATION WAS GIVEN TO THE RPTR ON WHY THE DELAY TO REWIRE THIS AIRPLANE AND 6 OTHERS WIRED INCORRECTLY. RPTR HAS 22 YRS EXPERIENCE AS AN A&P MECH. RPTR WAS NOT CONTACTED BY THE FAA.