Our Auto Pilot ST4000+ always did something(self Test?) in standby as soon as it was powered up and seems to work O.K. We have rudder control so we see where the rudder is on the display. About a month ago, we startd to experience a problem when underway and engaging the auto pilot. The wheel would turn the boat all the way to the port side and then all the way to the starboard side and then back and forth. I contacted Raymarine and described the issue to them. They said it sounded like something was wrong with the rudder control and suggested that I disconnect the wires to the ST4000+ from the rudder control. After I did this, it seemed that the problem was solved except that there was no display for the rudder control. So, I reconnected the wire to the rudder control and turned the power on. Now the screen showed the position of the rudder and there were no problems. We took the boat out and gave it quick 40 degree changes in course (push the 10 button four time) and it performed very well(better than before). The boat tracked, we did the swing test and it had the correct heading. It seems better than it was before the problem. However, now there is no self test(activity in standby when first powered up). Raymarine says with rudder control we don't need a self test for the unit to determine where the rudder is. Do any of you have the type of autopilot with rudder control? If so, does your's do the self test?