As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE TO CLT, ON FLIGHT NR 3478, WEATHER RADAR STARTED TO PAIN SPIKES THEN GOT PROGRESSIVELY WORSE. THERE WERE THUNDERSTORMS AHEAD. AIR RETURN TO DTW. MAINTENANCE REPLACED TCAS COMPUTER P/N/OFF & ON 622-8971-020, SN/OFF 6770 SN/ON 5613. ALL CHECKS GOOD AT THIS TIME IAW RH-85 MM CHAP 34.