As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4014 DURING THE CLIMB THE CREW REPORTED SMOKE AND ELECTRICAL BURNING ODOR IN THE COCKPIT. THE CREW DECLARED AN EMERGENCY AND RETURNED TO ORD. THE AIRCRAFT LANDED WITHOUT INCIDENT. AFTER TROUBLESHOOTING FOUND NR 1 PACK AIR CONDITIONING UNIT INOPERABLE. REMOVED AND REPLACED THE NR 1 AIR CYCLE MACHINE IAW EMB 145 AMM 21-51-03. THE OPERATIONAL CHECK AND LEAK CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.