As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON GROUND WITH PACKS AND BLEEDS NORMAL, COCKPIT AIR TEMPERATURE BECAME UNCONTROLABLE AND CLIMBED TO 70'C. COCKPIT TEMP SELECTOR HAD NO EFFECT, SHUT THE LEFT PACK OFF AND RETURNED TO GATE. ACFT GROUNDED. COMPLIED WITH TSR701248. FOUND THE LT ACM SEIZED. REMOVED AND REPLACED THE ACM IAW AMM 21-51-04. OPS AND LEAK CHECKED GOOD.