As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT MADE A PL FOR AN UNUSUAL NOISE IN THE CABIN AND NO PATIENT ON BOARD. MECHANIC INSPECTED AIRCRAFT AND FROM DESCRIPTION OF THE NOISE SUSPECTED AIR CONDITIONER BLOWER. PERFORMED RUN UP OF AIRCRAFT AND COUL NOT DUPLICATE NOISE. ACFT RETURNED TO SERVICE.