What was found
(CAN) FLIGHT CREW REPORTED CABIN PAC SUPPLY DUCT TEMP VERY HOT AND UNCONTROLLABLE IN CRUISE. INVESTIGATION OF ENVIRONMENTAL SYS FOUND CABIN ACM SEIZED. UNIT WAS REPLACED WITH OVERHAULED UNIT AND GROUND TESTED SERVICEABLE IAW AMM 12 AND 21. ACFT PRODUCT SUPPORT WAS CONTACTED TO REVIEW ACM FAILURE RATES. MFG INDICATED A NORMAL LIFESPAN OF ACMS IN THIS APPLICATION IS APPROX 750 A/F HRS. (TC 20100219010)