As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTS THAT HE HAD INTERMITTENT LOW ROTOR RPM WARNING SIGNALS WITH NORMAL ROTOR SPEED INDICATIONS. THE MAGNETIC PICKUP HAD A LOW ROTOR WARNING CIRCUIT COB. CONTINUITY PROBLEM. A NEW SENSOR WAS INSTALLED AND NO FURTHER DEFECT WAS REPORTED. SUGGEST A MORE ROBUST SENSOR BE DESIGNED AS THE COIL WIRES ARE HAIR THIN AND FAIL ROUTINELY. PERHAPS EVEN AN OPTIC SENSOR WOULD BE MORE RELIABLE. (K)