As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT TO PICKUP PATIENT, ROTOR TACH NEEDLE INDICATED ZERO. ABORTED FLIGHT AND NOTIFIED MECHANIC. RETURNED TO BASE FOR MAINTENANCE. DURING TROUBLESHOOTING, MECHANIC CLEANED CONNECTIONS AT THE MAG PICKUP AND THE TRIPLE TACH. OPERATIONAL CHECK AND GROUND RUN SUCCESSFUL. NO DEFECTS NOTED.