What was found
BTV - FLT 4856 - DURING DESCENT THROUGH HEAVY PRECIPITATION, THE CREW HAD A LEFT HAND INTAKE HEAT FAIL LIGHT ILLUMINATE. CREW LOOKED OUT THE WINDOW AND NOTICED SPARKS COMING FROM THE LOWER DUCT. AFTER SELECTING LEFT HAND INTAKE HEAT OFF PER CHECKLIST, SPARKS STOPPED AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LOWER DUCT, AND FOR PRECAUTIONARY REASONS, CHANGED THE THERMAL CONTROLLER, LOAD MONITOR, AND THE LOWER DUCT POWER RELAY. AFTER PERFORMING ALL CHECKS, THE AIRCRAFT WAS RETURNED TO SERVICE. (X)