What was found
RETURNED TO DEPARTURE, DUE TO EQUIPMENT COOLING ANOMALIES. ON REACHING CRUISE ALTITUDE, CREW REPORTED VENT EXTRACT FAN FAULT. CYCLED WITH MAINTENANCE CONCURRENCE, FAULT REMAINED. EMERGENCY DECLARED AND LANDED. MAINTENANCE REPLACED THE EXTRACT FAN IAW AMM 21-26-51. ACCOMPLISHED OPERATIONS TEST OF VENTILATION SYSTEM IAW AMM 21-26-00.