As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A GROUND OUT CHECK OF THE IGNITION SWITCH, THE ENGINE CONTINUED TO RUN. REPEATED TESTS DUPLICATED CONDITION 4 OUT OF 10 TIMES. UPON FURTHER INVESTIGATION IT WAS FOUND THAT THE RT MAGNETO CONTINUED TO RUN WHEN THE FAULT OCCURRED. REPLACED THE MAGNETO/STARTER SWITCH. MAGNETO SWITCH, MODEL NR A-510-9. AC PN C292501-0107, CAGE NR 65873.