st4000 autopilot

[Bobg]

Been having autopilot trouble this year, have read the archieves extensivly and couldn't duplicate my problem so would like to ask the members for advice before I call factory for assistance.  My problem is that the autopilot won't hold course, I can steer by pushing the +or -1, or + or - 10 port or starboard, and the pilot will respond, so I don't think it is a clutch issue or belt issue.

I have followed the book and and got to the step where I do the slow circle many times, the unit is suppose to "beep" when I do this before I move on to another step, it never beeps, but when I do move on to another step in the caliberation process anyway, it it says my devieation is 8 degrees. I go to the next step and set the screen numbers to match the pedistal compass and should be good to go according to the book, but it still doesn't work.  when I put it in auto and engage the clutch, the boat just wanders, even though course corrections are being made by the autopilot, but adjust no where near where I initially set the course. I have checked the head for water intrusion and it is dry, compass is located in the forward bilge by the mast step.
This unit has worked good for many years, except for halfway into this summer.

when in standby, shouldn't the degree numbers on the screen change when the boat turns to match the pedestal compass?  if it should it does not do that.  Thanks everyone  Bob

[Jim Hardesty]

Check the fluxgate compass.  Have you added anything near it thats magnetic?  ie speakers.  There may be a problem with the wire/connectors from the fluxgate compass to the control.  Check that they haven't been crushed and that the connections are clean and tight.
That's my first thought.
Jim