As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT DURING PREFLIGHT CHECKS THAT THE RUDDER TRIM WOULD NOT TEST WHILE ON AIRCRAFT BATTERY POWER, BUT WOULD TEST WITH EXTERNAL POWER APPLIED TO AIRCRAFT. TROUBLESHOOTING FOUND THAT THE TRIM ACTUATOR WAS DEFECTIVE. REMOVED THE RUDDER TRIM ACTUATOR P/N 45AS61014-111 (105) S/N 981002. INSTALLED A REPAIRED UNIT PER THE BEECH 400A AMM 27-20-00-201. FUNCTIONAL CHECKS WERE SATISFACTORY.