As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF LEFT PROP RPM INDICATOR INDICATED ZERO CYCLED C/B J-8, INDICATOR STILL INDICATED ZERO. WHILE RETURNING TO DTW INDICATOR WORKED INTERMITTENTLY. AIR RETURN TO DTW. MAINTENANCE REMOVED AND REPLACED GAUGE P/N 10223N01R00, S/N OFF 117, S/N ON BG05.