As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU CONTINUALLY SHUTS DOWN. AFTER REMOVAL AND REPLACEMENT OF COOLER BYPASS VALVE, INSPECTED ALL CHIP DETECTORS AND FILTER BYPASS PINS. ALL CKD GOOD. RAN APU UNLOADED FOR 20 MIN. NO FAULTS. RAN APU 45 MIN UNDER ELEC AND PNEUMATIC LOAD. OPS CK GOOD. (K)