As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - FLT 1951 - AFTER TAKEOFF ORD DURING CLIMB-OUT, ACRID ELECTRICAL ODOR NOTED IN CABIN AND COCKPIT WITH NO VISIBLE SMOKE. AIRCRAFT RETURNED TO ORD AND LANDED WITHOUT INCIDENT. OPERATED FANS AND AIR CONDITIONING PACKS WITH NO DEFECTS NOTED. UNABLE TO DUPLICATE ODOR. PRECAUTIONARY REPLACED LEFT AND RIGHT COALESCER BAGS. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)