What was found
AIRCRAFT WAS GROUNDED: FLIGHT DIVERTED TO ORD ON ACCOUNT OF ELECTRICAL SYSTEM ISSUE. EMERGENCY DECLARED. FLIGHT NOT OVERWEIGHT AND LANDED WITHOUT INCIDENT. ALSO, APU AUTO-SHUTDOWN AFTER APPROX. 10 MINUTES OF OPERATION. MAINTENANCE TROUBLESHOT IAW TSM 24-00-00-810-819-A. REMOVED AND REPLACED GLC 1 (9XU1) IAW AMM 24-22-55. RAN BOTH ENGINES AND TAXIED THE A/C FOR OVER 30 MINUTES. OPS CHECK GOOD. COULD NOT DUPLICATE FAULTS. PERFORMED OPS CHECK OF APU IAW AMM 49-00-00. OPS CHECK GOOD AT THIS TIME.