As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
L SIDE WINDOW HEAT "OVERHEAT" ILLUMINATED. GROUNDED - YES. PER B737-9 IFIM 30-41-00-810-827 WHCU LEFT SIDE HAD NO POWER. CIRCUIT BREAKER WAS OUT. RESET CIRCUIT BREAKER. PERFORMED WHCU BITE. NO FAULTS. PERFORMED WINDOW HEAT TEST. TEST GOOD.