What was found
JUST PRIOR TO LEVEL OFF AT 13000, STEADY WING OVERHEAT ANNUNCIATOR LIGHT CAME ON AND SMALL AMOUNT OF SMOKE CAME INTO THE CABIN. THE PILOT WENT THROUGH THE MEMORY ITEMS AND CHECKLIST AND THE LIGHT WENT OUT AND NO MORE SMOKE. RETURNED TO THE DEPARTURE AIRPORT. PHOENIX ATC ESCALATED TO AN EMERGENCY CATEGORY AND THE AIRCRAFT LANDED SAFELY WITHOUT INCIDENT. PHX MAINTENANCE INSPECTED CARGO BAY AND RIGHT WING FOR BLEED LEAKAGE, NO LEAK WAS FOUND. PERFORMED GROUND RUN, FOUND RT ACM COOLING TURBINE WAS SEIZED. RT ACM WAS BEING DEFERRED UNDER FLOW CONTROL VALVE SYSTEM, PER MEL 21-4. PART ON ORDER.