As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ROTATION ON A BLEED OFF T/O WE RETURNED THE PACKS TO NORMAL AND IMMEDIATELY SMELLED A BURNING, HEARD A LOUD HUMMING AND THE FLT DECK TEMP WENT FULL HOT. FOUND LEFT ACM FROZEN (LOCKED UP). REMOVED AND REPLACED LEFT ACM REF AMM 21-51-04; NEEDS OPS AND LEAK CHECK PER AMM 21-51-04. PERFORMED LEFT AIR CYCLE MACHINE INSTALLATION TEST IAW AMM 21-51-04-400-801 OPS AND LEAK CHECK GOOD.