What was found
YAW ACTUATOR FAIL CAUTION UPON TAXING THE AIRCRAFT. RETURNED TO PARKING AND MAINTENANCE RESET THE CAUTION AND IT WORKED FOR APPROXIMATELY 5 MIN AND FAILED AGAIN IN FLIGHT. AIRBUS RESET PERFORMED ON 3RD ATTEMPT, IT CLEARED THE CAUTION AND LATER FAILED A THIRD TIME. FTR AND TRIMS ON OR OFF DID NOT MAKE ANY DIFFERENCE. DURING TROUBLESHOOTING FOUND WHEN FAULT IS PRESENT (ACTUATOR LIGHT YAW IN AMBER) 28 VOLTS MISSING ON PIN 17 OF BREAKOUT BOX. REPLACED YAW SEMA IAW AMM 67-20-00, 4-8. T/F COMPLETE.