"It sounds like the autopilot computer has lost the flux gate compass calibration. This almost certainly has nothing to do with the C90W. It is just responding to the messages coming from the autopilot course computer. Look in the manual of the course computer and see how to recalibrate the flux gate compass. It involves driving the boat in circles typically.
It is also possible that the compass declination setting in the C90W has been changed but that is unlikely. Typically this setting will be set to the automatic feature and it then gets the declination from the GPS
There may be some kind of memory failure of the autopilot but sometimes in rare circumstances the calibration data is simply lost. Did anything happen such as some kind of electronic disturbing event such as lightning
or some DC electrical
Transmitter Dan - Thank you so much for your response. The PO told me that he had the flux gate compass replaced last year when the autopilot would suddenly head
the boat on a reciprocal heading. That seemed to fix the problem but I did notice the auto pilot "dropping off line" several times while ferrying the boat to Alaska
. I didn't think much of it but possibly it was telling me of a coming problem. The auto pilot will follow a heading, but it's the reciprocal of where it's actually going. I really appreciate that the problem is not likely to the the C90W. I will find the documentation
about re-calibrating the flux gate compass and follow that procedure. I noticed when I was trying to figure the problem out on the display, the compass correction values were missing and there was no way to manually enter corrections if I had them.
There were no electrical storms at any time since getting the boat and I'm not aware of any electrical anomalies or events
on the boat.
It will be a couple of weeks before I'll be on the boat again but I'll let you know how things turn out. Thanks again for your response.