As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ELECTRICAL PREHEAT SYSTEM WIRING SMOKE AND SPARKS NOTED AFTER MOVING AIRCRAFT INTO HANGAR. WHILE CONNECTING 115 VOLT SHORE POWER TO SYSTEM CRACKLING NOISE AND SMOKE DETECTED FROM WIRING JUNCTION BLOCK IN MGB AREA. JUNCTION BLOCK OVERHEATED MELTING HEAT SHRINK AND WIRE INSULATION. NO DAMAGE TO ANY SURROUNDING AREA.