F03505 fault in siemens 6RA80 DC Drive indicate Analog input wire breakage. This means the wire-break monitoring for an analog input has responded. The input current of the analog input has exceeded the threshold value parameterized in p4061[x]

1. Check the wiring for interruptions.
2. Check the magnitude of the injected current - it is possible that the infed signal is too low.
3. Check the load resistor (250 Ohm).