Raymarine St4000 autopilot ... Freaking out

[smac999]

try doing a compass calibration (donuts) and see if it passes or fails.

never mind old thread...

[pgenovese]

Hi Rhumbline,

I suspect you may be right about the corrosion, shortly after I had posted my original post I had taken apart, cleaned and protected all connectors on my Raymarine system with Anti Corrosive Gel and have not had another "incident" since then.

[Air Raiders]

Ditto,

Exact same problem while offshore at Washington State, Strait of Juan De fuca. boat turned east 90 degrees and started heading for shore without any indication of a problem. Shortly after the autopilot drive completely stopped working. I traced problem down to a failure of the + and/or - motor drive signal at the back of the St4000 unit. I think these units may be getting into a condition when the positive or Negative power drivers start failing, otherwise the power drive transistor intermittantly starts swinging between +12 and ground, even though its getting the correct bias input signal. However this is just a theory at this point.

[senormechanico]

Mine is a 4000 not a 400+ and I had similar symptoms.

For the fix, I had to resolder all four of the power transistor connections in the control head.
Out of 12 connections, 9 were bad.