As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW NOTICED SMOKE IN COCKPIT AND CABIN WHEN RUNNING THE AIR SOURCE OFF THE APU. PERFORMED FRICTION TEST ON ACM, IAW CMM 21-52-57-700-801 AND FOUND ACM TURBINE SEIZED. REMOVED AND REPLACED ACM, IAW BD 100 AMM 21-52-13-400-801. LEAK TEST AND OPERATIONS TEST PERFORMED, IAW AMM 21-52-00-710-801, NO DEFECTS NOTED. P/N 3471A020000; S/N 00155.