What was found
DIVERTED, APU AUTO SHUT DOWN & DEFERRED GENERATOR. APU 1660 HAS NO HISTORY SINCE INSTALLATION - FIRST HIT LAST SHOP VISIT 12APR05 NEW LOW OIL PRESSURE SWITCH & CONFIGURATION INSTALLED. APU HAS 661 HRS. TSHM & 890 CSHM. SFOEP CAPTURED UNIT & COMMUNICATED DATA PLATE INFO TO VENDOR FOR INTENSIVE INVESTIGATION. AFTER MANY YEARS OF DEVELOPMENT & TESTING THERE HAS BEEN THREE FAILURES OF THE NEW LOP SWITCH WHICH IS UNDER INVESTIGATION. TWO OF THE FAILURES OCCURRED ON SAME ENGINE. DISCOVERED GEARBOX OIL PRESSURE WAS FLUCTUATING EXCESSIVELY. THIS FLUCTUATION ACTS LIKE A HAMMER ON THE LOP SWITCH DIAPHRAGM EVENTUALLY RUPTURING IT. APPEARING LIKE A SWITCH FAILURE WHICH WAS ACTUALLY THE RESULT OF AN ACTION.