As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT SIDE WINDOW HEAT "OVERHEAT" LIGHT ILLUMINATED IN CRUISE AT FL 400. FOLLOWED AND TURNED OFF FOR 5 MIN. TURNED BACK ON STILL ILLUMINATED. SWITCHED BACK OFF. SHOOK LT SLIDING WINDOW COIL CORD. UNABLE TO DUPLICATE. DUE TO HISTORY REMOVED LT WINDOW HEAT CONTROL UNIT PER FIM 30 41 11 000 801. INSTALLED WHCU PER FIM 30 41 11 400 801. OPS CHECK GOOD ON GROUND. VERIFIED ETOPS PART INSTALLED PER IPC.