As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO CONTROL TEMP CABIN AND FLT DECK IN ANY SELECTION. MANUAL-AUTO RECYCLED PACKS OFF-ON. NO CHANGE. FOUND LT PACK BYPASS VALVE FAILED TO FULL HOT WITH ZERO MA FULL COLD INPUT. REPLACED LT PACK BYPASS VALVE IAW AMM 21-51-31-000-801+ 21-51-31-400-801 TESTS GOOD. RETURNED TO SERVICE.