As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 400 - PHX-SFO - BURNING SMELL - GRINDING SOUND FOLLOWED BY THE SMELL OF RUBBER / ELECTRICAL SMOKE, 1 HOUR INTO A 2 HOUR FLIGHT. SMELL ONLY LASTED A SHORT TIME. CONFIRMED NR 2 PACK OVERHEAT. REMOVED AND REPLACED PACK NR 2 AIR CYCLE MACHINE (ACM) PER AMM21-52-21, LEAK & OPERATIONAL CHECK WAS GOOD.