As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER RUNNING APU FOR 15 MINUTES, CABIN FILLED WITH SMOKE AND SMELLED LIKE BURNED MATCHES OR RUBBER. SHUT PACS AND APU OFF. TROUBLESHOT TO ACM. OIL BLACK AND SHAFT IS NOT SMOOTH WHEN TURNED. ODOR ONLY OCCURS WHEN CABIN PAC IS SELECTED. REMOVED AND REPLACED ACM WITH REPAIRED UNIT. SERVICED OIL AND OPS/LEAKS CHECKS GOOD.