As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STALL WARNING SYSTEM FUNCTION TEST AT ANNUAL INSPECTION WAS CORRECT. SYSTEM WOULD NOT OPERATE WHEN PITOT HEAT WAS SWITCHED ON. REMOVED STALL SWITCH AND CLEANED CORROSION FROM GROUND. BOTH STALL WARNING AND PITOT HEAT WOULD OPERATE CORRECTLY THEN. PREVIOUSLY, THE STALL WARNING SYSTEM WOULD FIND A GROUND THROUGH THE PITOT HEATER VIA THE STALL WARNING HEATER. WHEN THE PITOT HEAT WAS TURNED ON, THE STALL WARNING WOULD NOT GROUND.