As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED, AFTER DEPARTING, TURNED THE AIR CONDITIONING FAN ON AND WHEN IN CRUISE HE NOTICED A SPARK FALL FROM UNDERNEATH THE INSTRUMENT PANEL NEXT TO THE LT SIDE OF THE INSTRUMENT BULKHEAD (RT ANTI-TORQUE PEDAL AREA). MADE A LEFT TURN DIRECT TO DEPARTURE AIRPORT. THEN TURNED THE AIR CONDITIONING FAN OFF AS A PRECAUTIONARY MEASURE AND NOTIFIED MX. MECHANIC INSPECTED AREA AND FOUND POWER WIRE TO THE FAN SWITCH CHAFING, CAUSING THE SPARK.