What was found
AFTER STARTING THE ENGINES, THE YAW SAS AND BACKUP SAS CAUTIONS WERE DISPLAYED ON THE CAD. WHILE PERFORMING THE AP TEST THE YAW ACTUATOR KEPT FAILING THE TEST AND THE YAW SAS AND BACKUP SAS CAUTIONS WOULD NOT GO AWAY IF THE APS WERE OFF, BUT WHEN THE APS WERE TURNED ON THEN THE ACTUATOR CAUTION WOULD ILLUMINATE. DURING TROUBLESHOOTING FOUND YAW SEMA HAD A VALID SIGNAL IN WITH NO VALID SIGNAL OUT. WATER INTRUSION WAS NOTED WHEN DISCONNECTING THE YAW SEMA CANNON PLUG. REMOVED AND REPLACED SEMA ACTUATOR; MTF SUCCESSFULLY COMPLETED IAW RFM 29.1.