What was found
BWI - FLT 0166 - DURING CRUISE, EN ROUTE PHX/PHL, THE WEATHER RADAR BECAME UNRELIABLE. TEST PAGE SHOWED 'R/T FAULT' FOLLOWED BY 'NO WXR'. SYSTEM WORKED FINE INITIALLY. FLIGHT DIVERTED TO BWI AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE OPERATIONALLY CHECKED SYSTEM AND NOTED NO FAULTS FOUND. REMOVED AND REPLACED WEATHER RADAR TRANSCEIVER (P/N 2041217-0416) AS PRECAUTIONARY. OPS CHECK GOOD. (X)