[CA] [CA11] St70 AP heading about 40 degrees off from actual compas heading

[Tomoffmic]

Most of the summer my ST 70 AP heading has been about 65 degrees off from my actual compass heading. pretty much always read about 307 mag
When I engage AP tracking the boat does a hard starboard Crazy Ivan and I have to release AP and take back control.
Today I placed a large heavy magnent next to the GPS compass donw below and now its only about 40 degrees off. Did the large magnet some how un stick the heading or is the gps compass unit itself maybe bad?
I'm still trouble shooting this issue since early june. (Boat is new to us this year) St 70 AP with e120 HD display
Thanks

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Tom,

While the reported issue may be indicative of a problem with the autopilot's fluxgate compass, it is recommended that you first attempt to resolve this issue by inspecting the area around the fluxgate compass to ensure that no objects capable of producing a magnetic field have been placed or installed within 3' of the fluxgate compass. If not, then it is recommended that the autopilot's compass be re-calibrated to determined the sensed deviation and that the compass then be aligned to the proper heading. Information concerning how to perform these actions may be found within the SeaTrial Calibration section of Chapter 1.2: Commissioning procedures of the SPX Setup and Commissioning Guide.

Should the problem persist thereafter, then it would be recommended that the fluxgate compass be tested. If found to fail resistance checks or should a pause in the reported heading be observed when turning the vessel through a slow 360 degree turn, then the fluxgate compass should be replaced.