As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FWD LEFT WINDOW HEAT OVERHEAT IN FLIGHT ACCOMPLISHED QRH AND LIGHT STAYED EXTINGUISHED. GROUNDED - YES. REF B737-900 FIM 30-41 TASK 801, 30-41 TASK 812. WHCU SHOWS NO CURRENT FAULTS, HISTORY SHOWS VARIOUS #1 WINDOW SENSOR FAULT LT. ACCOMPLISHED WHCU OVERRIDE MODE. OPS TEST NORMAL. COULD NOT DUPLICATE ON GROUND.