What was found
(CAN) FLIGHT CREW REPORTED WING BODY OVERHEAT INDICATION LT AND RT CAME ON. LT WING - BODY OVERHEAT INDICATION EVENTUALLY EXTINGUISHED. LT WING BODY OVERHEAT INDICATION CAME ON AGAIN AFTER APPROXIMATELY 30 MINUTES AND RT PACK INDICATION ILLUMINATED. ALL 3 INDICATIONS, WING BODY OVERHEAT LT AND RT AND RT PACK STAYED ON FOR THE DURATION OF THE REMAINING FLIGHT. AS THE FLIGHT WAS RETURNING, AT FLIGHT LEVEL 350, BOTH CABIN ALTITUDE AND ASSOCIATED AURAL HORN WERE ACTIVATED. FLIGHT CREW USED O2 MASKS. AN EMERGENCY WAS DECLARED AND THE ACFT LANDED UNEVENTFULLY. AFTER LANDING BOTH WING BODY OVERHEAT LT AND RT EXTINGUISHED. MAINTENANCE PERSONNEL COMPLETED THE ASSOCIATED T/S AND FOUND IN RT PACK BAY A DUCT ASSY CRACKED AND BLOWN OPEN P/N:213A1501-73. DEFECTIVE ASSY DUCT REPLACED AND THE ACFT WAS RETURNED TO SERVICE WITH NO SIMILAR RECURRENCE.