As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CABIN A/C PACK UNCONTROLLABLE IN AUTO OR MANUAL. UNCONTROLLABLE HEAT WITH PACK ON. PACK OFF, TEMP DECREASES. SMOKE EMITTED INTO CABIN WHILE ON GROUND WITH APU RUNNING. FOUND CABIN ACM SEIZED. REMOVED & REPLACED THE OVERHEAD ACM. WORK DONE IAW MM 21-51-00. SYSTEM OPS CHECKED GOOD.