What was found
FLT#1621, LHR-BOS. (ETOPS) FUEL ACT XFR FAULT ((MEL 28-40-09I CAUTION ON ECAM 5) ACT XFR FAULT (ACT) ( CAUTION ON ECAM 5) ACT XFR FAULT (ACT). REMOVED AND REPLACED ACT VENT VALVE ACTUATOR (91QH) IAW AMM 28-28-72. PERFORMED OPS TEST OF THE ACT AUTOMATIC TRANSFER SYSTEM IAW AMM 28-28-710-005-A. ALL OPS TESTS OK. NO FAULTS NOTED. A/C RETURNED TO THE ORIGINAL GROUND CONFIGURATION. MDDR CLEARED. MX-4 UPDATED. PLACARD REMOVED. MCC NOTIFIED.