What was found
(CAN)DE-ICING CONTROL VALVE FAILED BECAUSE OF LACK OF DRAIN HOLE. IT HAD BEEN PLUGGED BY POTTING COMPOUND WHEN VALVE HEATERS WERE INSTALLED.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
(CAN)DE-ICING CONTROL VALVE FAILED BECAUSE OF LACK OF DRAIN HOLE. IT HAD BEEN PLUGGED BY POTTING COMPOUND WHEN VALVE HEATERS WERE INSTALLED.