Erratic output from ACU 400

[Andy Laws]

I have installed an ACU 400 and EV1 with a type 3 hydraulic linear drive on my boat which worked well for the first 12 hours or so but now is giving an erratic output. At first the drive would run the pump smoothly but now it is jerking the wheel sometimes violently with the output swinging rapidly between +/- 22 volts. I have tried 2 different rudder references and no rudder reference but it doesn’t change anything. When I changed the electronics I kept the old autopilot in place with a transfer switch so that it can be used as a stand alone back up incase of failure to the new autopilot or stng network. When I switch the system back to the old pilot it runs smoothly so I dont believe that it is a problem with the pump, rudder reference or power supply which just leaves the ACU 400 or EV 1. How can I troubleshoot them to see if they are functioning properly?