As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STARTED APU AND TURNED ON BLEED AIR. BOTH CABIN AND COCKPIT AIR SUPPLY TEMPS WENT TO 250. COULDN'T GET THE TEMPS LOWERED EITHER MANUALLY OR AUTOMATICALLY. CABIN BEGAN TO FILL WITH SMOKE AND HAD A PLASTIC BURNING ODOR. R & R SEIZED ACM COOLING TURBINE AND INSTALLED O/H COOLING TURBINE IAW MM 21-51-00. OPS/ LEAK CHECKS GOOD.