As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT FORWARD WINDOW HEAT LIGHT ILLUMINATED ON CLIMB OUT. PERFORMED QRH PROCEDURE AND LIGHT REMAINED EXTINGUISHED UNTIL AFTER LANDING SEATTLE. AFTER LANDING, LEFT FORWARD WINDOW HEAT ILLUMINATED AGAIN. GROUNDED-YES. REMOVED AND REPLACED LEFT FORWARD WINDOW (L1), REF B737-900 AMM 56-11-11/401. LEAK AND OPERATIONS CHECK PASSED.