As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN APU BLEED AIR IS SELECTED CABIN AND COCKPIT AREA BEGINS TO FILL WITH BLUE SMOKE. REMOVED ACM DUCTING & SEALS, R&R ACM. BEGAN INSTALLATION OF OVERHAULED ACM COMPLETED INSTALLED DUCTING, AND NEW SEALS. TORQUED AND/OR SAFETIED CLAMPS. INSTALLED APU ACCESS PANEL. RAN APU AND OPERATIONALLY CHECKED THE ENVIRONMENTAL CONTROL TEST. OPERATIONAL CHECK GOOD IAW MM 21-51-00.