As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6506 - IAD-BOS - DURING TAXI OUT, AIRCRAFT EXPERIENCED A DUCT OVERTEMP LIGHT ILLUMINATION. AIRCRAFT RETUREND TO THE GATE WHERE MAINTENANCE TROUBLESHOT THE DISCREPANCY AND FOUND THAT THE ACM HAD BECOME STUCK. MAINTENANCE FREED THE ACM AND RETURNED AND RELEASED THE AIRCRAFT FOR SERVICE. (M)