As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLT - FL 1754 - CLIMBING THROUGH 12,000 FEET, THE LEFT GENERATOR BECAME INOPERATIVE. THE APU WAS ON MEL. THE AIRCRAFT RETURNED TO THE FIELD WITHOUT INCIDENT. MAINTENANCE REPLACED THE LEFT GENERATOR AND THE APU GENERATOR CONTROL UNIT. THE SYSTEMS THEN OPERATED NORMALLY. REF: OPERATOR CONTROL NR USAAD98003.