autohelm ST4000 worked well until a month ago. When I power it on the helm goes hard over to turn the boat to port. I can press standby to stop it. I can adjust the helm back to center using the +10 and +1 keys. When I press autopilot key it steers hard over to port and refuses to pick up a magnetic course. The only variable I can think of is I used power tools nearby it in doing some fibreglass work. I have checked the calibrations and checked the electrical connections, they are good. Per a contact with Raymarine I held the standby key down for 10 seconds. No change. Any one have any ideas?