What was found
A LEFT HAND AIR CONDITIONING PACK OVERHEAT MESSAGE ILLUMINATED DURING THE TAXI OUT FOR TAKEOFF. THE CABIN FILLED WITH SMOKE. THE PACK WAS TURNED OFF AND THE SMOKE CLEARED THE CABIN. MAINTENANCE INSPECTED THE AIRCRAFT FOR A FERRY FLIGHT TO DAY FOR REPAIR. THE FERRY FLIGHT WAS CARRIED OUT WITHOUT ANY PROBLEMS. MAINTENANCE REMOVED AND REPLACED THE LEFT HAND AIR CONDITIONING ENVIROMENTAL CONTROL UNIT, IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 21-51-10. OPERATIONAL CHECKS WERE COMPLETED, AND THE AIRCRAFT WAS RETURNED TO SERVICE.