What was found
ON CLIMBOUT OF PHX EN ROUTE FOR LAS BOTH THE CAPTAINS AND FIRST OFFICERS WEATHER RADAR LOCKED IN TEST MODE, SWITCHING SYMBOL GENERATORS AND CYCLING TERRAIN SWITCHES, NO HELP. DUE TO WEATHER EN ROUTE, TURNED BACK TO PHX FOR REPAIR. MAINTENANCE REMOVED AND REPLACED WEATHER RADAR RECEIVER TRANSMITTER IAW BMM 34-43-01, OPERATIONAL CHECK WAS GOOD. FUNCTIONAL TEST OF WEATHER RADAR RECEIVER TRANSMITTER S/N 3652 WAS NO FAULT FOUND, PERFORMED A VISUAL INSPECTION OF UNIT, RETESTED, RETURNED TO SERVICE IAW CMM 34-45-21, REV. 009.