As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THE HORIZONAL STAB HEAT FAIL ANNUNCIATOR ILLUMINATED 3 SECONDS AFTER TURNING ON STAB HEATING SYSTEM AT FL350. NO VISIBLE MOISTURE. THE MAINTENANCE VENDOR TROUBLESHOT AND FOUND THE HORIZONTAL STAB DE-ICE CONTROLLER DEFECTIVE. THE DEFECTIVE CONTROLLER WAS REMOVED AND REPLACED WITH OVERHAULED UNIT. OPS CHECKS SATISFACTORY. THE AIRCRAFT WAS RETURNED TO SERVICE.