A CRJ200'S YAW DAMPERS DISENGAGED WITH FULL RT RUDDER APPLICATION DURING TAXI OUT. THIS EVENT HAPPENED TWICE BEFORE ACFT WAS REPLACED. THE CREW WOULD NOT FERRY THE ACFT FOR MAINT.

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DURING TAXI OUT PERFORMING THE TAXI CHKLISTS THE RUDDER INDICATIONS ON THE FLT CTL SYNOPTIC PAGE WOULD NOT SHOW FULL DEFLECTION TO EITHER THE L OR R SIDE WITH FULL RUDDER INPUTS. ALSO; DURING THIS RUDDER CHK WITH FULL R RUDDER APPLICATION BOTH YAW DAMPERS DISENGAGED. WE RESET THE YAW DAMPERS AND CHKED THE RUDDER WITH THE SAME RESULTS. MAINT WAS CONTACTED; WE RETURNED TO THE SAME GATE; AND A DISCREPANCY WAS ENTERED IN THE ACFT LOGBOOK. MAINT DEFERRED THE RUDDER INDICATION SYS AND RESET THE YAW DAMPER SYS. WE AGAIN TAXIED OUT AND DURING THE FLT CTL TAXI CHK THE YAW DAMPERS DISENGAGED WITH FULL R RUDDER APPLICATION. MAINT WAS CALLED; RETURNED TO THE GATE; AND AGAIN ENTERED A DISCREPANCY IN THE ACFT LOGBOOK. THE PAX WERE OFFLOADED AND MAINT WANTED US TO PERFORM THE FLT CTL CHKS WITH A MECH ON BOARD. DURING THE TAXI CHKS THE YAW DAMPERS DISENGAGED WITH FULL R RUDDER APPLICATION WHEN EITHER BOTH OR SINGLE YAW DAMPER WAS ENGAGED. ACR MAINT CTL ASKED IF WE WOULD BE COMFORTABLE FERRYING THE ACFT TO ZZZ. AFTER DISCUSSION THE SITUATION WITH MY FO WE CAME TO THE CONCLUSION THAT IT WOULD BE UNSAFE AND EXCEEDED OUR COMFORT ZONE. LATER; A NEW ACFT WAS ASSIGNED AND THE FLT SEGMENT WAS COMPLETED.