What was found
(CAN) FLOW LIGHT (PRESSURIZATION) CAME ON AFTER TAKEOFF. AIRCRAFT LANDED BACK FROM DEPARTURE. MAINTENANCE FOUND ONE CLAMP NOT PROPERLY INSTALLED ON OUTLET OF LT ACM. ACM WAS PREVIOUSLY REPLACED FOLLOWING DISCREPANCY. CLAMP HAS BEEN SECURED FOLLOWED WITH PRESSURIZATION TEST AND AIRCRAFT DISPATCHED SERVICEABLE. A SECOND AIR TURNBACK HAPPENED THE FOLLOWING DAY FOR THE SAME REASON (PRESSURE FLOW LIGHT ON). MAINTENANCE FOUND THE LT ACM SEIZED. ACM HAS BEEN REPLACED. ACM IS UNDER INVESTIGATION.