As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WINDOW HEAT L SIDE OVERHEAT LIGHT ILLUMINATED IN FLIGHT. FOLLOWED QRH PROCEDURE AND OVERHEAT LIGHT ILLUMINATED AGAIN. GROUNDED - YES. PERFORMED WHCU BITE PROCEDURE PER B737-900 FIM 30-41 TASK 801 NO CURRENT FAULTS NOTED OK FOR SERVICE ALL OPS GOOD.