As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3936 -ATB/FUMES- RETURNED TO ATL DUE TO BURNING ODOR IN COCKPIT AFTER TAKEOFF. CONTROL CABIN ZONE TEMP LIGHT ILLUMINATED. CORRECTIVE ACTION: #2 ZONE TEMP CONTROLLER FAULTS COCKPIT TRIM AIR VALVE. REPLACED SAME AND RECIRCULATION FILTERS. OPS CHECKS GOOD.