As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 4253 - AFTER TAKEOFF, THE LEFT BLEED AIR OVERPRESSURE LIGHT ILLUMINATED AND THE BLEED VALVE CLOSED. AIRCRAFT RETURNED TO BOS AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE LEFT BLEED OVERPRESSURE SWITCH HAD FAILED. SWITCH WAS REPLACED AND SYSTEM CHECKED GOOD. (M)