As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 4324 - AFTER TAKEOFF, THE MAIN PASSENGER DOOR WARNING LIGHT ILLUMINATED. AIRCRAFT RETURNED TO BOS AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND DOOR HANDLE SWITCH AND FAILED. SWITCH WAS REPLACED AND AIRCRAFT RETURNED TO SERVICE. (M)