What was found
EMERGENCY DECLARED DESCENDING THRU APPROXIMATELY 11000, APT FAULTS, APU AUTO SHUTDOWN RESULTING IN SINGLE ELECTRICAL SOURCE. RAN QRT ,APU CAME BACK UP ONLINE. PREVIOUS RESET APU GENERATOR SO WE DID NOT ATTEMPT A SECOND PER FIM 24-20 TASK 805, REPLACED APU GCU PER AMM 24-22-02. STARTED UP AND RAN APU SEVERAL TIMES, UNDERSPEED FAULT NEVER RETURNED (AMM 49-11-00-802-008). FOUND FAULT A/C STRT CIRCUIT, FOUND APU STARTER WIRE LOOSE CONNECTION AT STARTER. TIGHTENED, FAULT CLEARED AND DID NOT RETURN.