B737 CREW FOUND PAX OXYGEN MANUAL DEPLOYMENT SWITCH GUARDS SAFETY WIRED WITH NON-FRANGIBLE SAFETY WIRE ON PREFLT.

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DURING PREFLT FLT DECK SET-UP; DISCOVERED PAX OXYGEN MANUAL DEPLOYMENT SWITCH GUARD HAD BEEN SAFETY WIRED WITH NON-FRANGIBLE HVY WIRE. LOGBOOK ENTRY ACCOMPLISHED; MAINT NOTIFIED. WHEN MAINT TECHNICIAN ARRIVED AT ACFT HE CONFIRMED NONSTANDARD WIRE AND THEN WE ATTEMPTED TO MANUALLY BREAK THE INSTALLED WIRE WITH NO SUCCESS. MAINT TECHNICIAN REMOVED NON-FRANGIBLE WIRE AND INSTALLED PROPER WIRE. I SUGGEST: 1) DETERMINE THE HISTORY AND IF THIS WAS A CONTRACT MAINT ISSUE THAT COULD HAVE BEEN APPLIED IMPROPERLY TO OTHER ACFT IN OUR FLEET. 2) DUE TO THE SERIOUS SAFETY RAMIFICATIONS OF IMPROPER WIRE BEING INSTALLED; INITIATE AN IMMEDIATE FLEET WIDE INSPECTION TO CORRECT ANY PROBS AND IMPROPER INSTALLATIONS. DURING THAT INSPECTION; REVIEW PROPER SAFETY WIRE FOR CSD/IDG SWITCH GUARDS; AND THE ALTERNATE FLAPS MASTER SWITCH GUARD. 3) I HAVE OBSERVED IMPROPER SIZED SAFETY WIRE THAT HAS BEEN INSTALLED RANDOMLY ON ACFT I HAVE BEEN ASSIGNED SINCE OCT/2000. IN ALL CASES; THE WIRE WAS TOO LARGE AND NOT FRANGIBLE WHICH COULD HAVE CONTRIBUTED TO AN INABILITY TO ACCOMPLISH ABNORMAL OR EMER PROCS. A REVIEW OF MAINT PROC FOR BOTH 'IN HOUSE' AND CONTRACT VENDORS SHOULD BE CONSIDERED TO PRECLUDE INFLT EMERS.