What was found
AIRCRAFT LOST PRESSURIZATION ABOVE 15,000 FT WITH PRESSURIZATION INDICATIONS TURNING RED AND OXYGEN MASKS DEPLOYING. TROUBLESHOT IN REF TO FIM 21-31-00-810-809-A. PRESSURIZED A/C, IAW AMM 21-31-00 USING APU FOR PNEUMATIC ENERGY IAW AMM 36-00-00-860-802-A/200, NO DEFECTS NOTED. PRESSURIZED A/C USING ENGINES FOR PNEUMATIC ENERGY, IAW AMM 36-00-00-860-801-A/200, NO DEFECTS NOTED. UPON FURTHER INVESTIGATING WIRE HARNESS W407 ON NR 1 ENGINE FOUND TO BE DETERIORATED AND SOME CORROSION FOUND IN SWITCH. R & R NR 1 HIGH STAGE PRESSURE SWITCH, IN REF TO AMM SECTION 36-11-07-04. R & R WIRING HARNESS W407 IN REV TO PPBM SECTION 71-00-00. PERFORMED FUNCTIONAL TEST, IAW AMM 36-11-02-700-801-A. OPERATIONS CHECK GOOD.