As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LHR - CREW REPORTED FORWARD EQUIPMENT EXHAUST FAN CAME ON FOLLOWED BY ELECTRICAL BURNING ODOR FOR BRIEF TIME. FLIGHT LANDED LHR WITHOUT INCIDENT. FORWARD EQUIPMENT EXHAUST FAN DEFERRED PER MEL. REPLACED FORWARD EQUIPMENT EXHAUST FAN AT MIA ON 09/11/2012. SYSTEM GROUND CHECK NORMAL OPERATION.