As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT FWD WINDOW HEAT OVERHEAT LIGHT ON ON THE GROUND EXECUTED QRH PROCEDURE LIGHT EXTINGUISHED. GROUNDED - YES. PERFORMED LAMP TEST OF WHCU #1 FOUND LIGHTS #1 NOT ILLUMINATED, PULLED AND RESET C/B B21 ON P6-5 PANEL OPS CHK NORMAL. BITE CHK OK PER B737-9 AMM 30-41-11-400-801.