As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FWD CABIN TEMP CONTROL ERRATIC WITH KNOB AT THE 9 O'CLOCK POSITION. TEMP WENT FROM 20C TO 60C UNCOMMANDED. TEMP DID RESPOND TO FULL COLD SECTION. ACFT GROUNDED. INTERROGATED THE LT ZONE TEMP CONTROLLER, FOUND LT PACK TCV FAILED. REMOVED AND REPLACED THE LT PACK TEMPERATURE CONTROL VALVE IAW AMM 21-51-10. OPS CHECKED NORMAL. NO FAULTS LOGGED AFTER TEST. OPERATED FWD CABIN TEMP CONTROL THROUGH FULL TEMP RANGE. OK FOR SERVICE.