As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 6330 - IAD-PIT - DURING CLIMB-OUT, RETURNED TO IAD DUE TO THE LEFT DUCT FAIL LIGHT ILLUMINATING. AIRCRAFT LANDED AT IAD WITH NO FURTHER INCIDENTS. MAINTENANCE REPLACED THE O-RINGS ON THE LEFT ENGINE BLEED DUCT COUPLING. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)