As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON INSTALLATION OF THE OVERHAULED MAGNETO IN THE AIRCRAFT, THE TACHOMETER DID NOT WORK. FURTHER INVESTIGATION REVEALED THAT THE TACHOMETER POINTS HAD ZERO CONTINUITY BETWEEN THE TERMINALS AND THE POINTS. REPLACED THE TACHOMETER POINTS AND THE TACHOMETER WORKED FINE.