As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6320 - IAD-RDU - DURING TAXI, RETURNED TO GATE DUE TO LEFT DUCT FAIL LIGHT ILLUMINATED. MAINTENANCE INSPECTED AND REMOVED AND REPLACED BLEED AIR COUPLING O-RING, OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)