As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PACK FAILED ON TAKEOFF WITH PACK INOP AND PACK OFF DISPLAYED RESET NORMAL BUT HAD PLASTIC BURNING SMELL AND ALSO A RATTLING SOUND IN DUCTING AREA ABOVE SEAT 9C. CREW SELECTED PACK OFF AGAIN AND BURNING SMELL AND RATTLE STOPPED. FOUND LEFT PACK CONTROL VALVE NOT OPENING FULLY FOUND PLASTIC IN BUSINESS CLASS WARMING OVEN, REMOVED PLASTIC. REPLACED VALVE PER MM 21-51-01. PACK OPS CHECKS NORMAL. AC OK FOR SERVICE.