What was found
FLIGHT RETURNED TO DEPARTURE DUE TO SEVERAL LARGE UNCOMMANDED YAW - RUDDER INPUTS REPORTED WHILE CLIMBING THROUGH 16K FT. THE AUTOPILOT DISENGAGED AND THE DFGC SYSTEM CIRCUIT BREAKER C18 OPENED AND WOULD NOT RESET. BOTH MCP AND AUTOTHROTTLE FUNCTIONS WERE LOST. SPURIOUS YAW INPUTS CONTINUED UNTIL THE YAW DAMP SWITCH WAS TURNED OFF AND THEN THE UNCOMMANDED YAW INPUTS CEASED. T/S IAW WDM AND INSPECTED RUDDER POSITION CIRCUIT. FOUND WIRE 20610X22RD WAS SHORTED TO ACFT GROUND. WAS ABLE TO DUPLICATE PILOT WRITE-UP. REPAIRED WIRE IAW SWPM CH 20. RAN RTS CHECKED GO. THE ACFT HAS RETURNED TO SERVICE.