As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPTAIN SIDE WINDSHIELD POWER TERMINAL BLOCK SPARKED AND CAUGHT FIRE IN FLIGHT ON DEPARTURE OUT OF YYZ. FIRST OFFICER TURNED OFF WINDSHIELD HEAT & FIRE STOPPED. RETURNED TO YYZ. FOUND HEATER POWER TERMINALS P1 & P2 OPEN AND EXCESSIVE HEAT/FUME DEPOSIT ON LH WINDSHIELD. REMOVED AND REPLACED LH WINDSHIELD IAW JC 900-56-900-901. OPS CK GOOD.