As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING FLIGHT THE COPILOTS A WINDSCREEN DID NOT HEAT. THE MAINTENANCE TEAM DETERMINED THAT THE THERMAL CONTROLLER WAS DEFECTIVE. THE DEFECTIVE CONTROLLER WAS REMOVED AND A NEW UNIT WAS INSTALLED. OPERATIONAL CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.