autopilot will not calibrate

[jkdoyle]

Hello,
I own a Raymarine autopilot (S1 computer and ST6001 controller). The autopilot worked flawlessly last year. I noted early this year that the fluxgate compass reading was about about 180 degrees from the magnetic compass reading.I swung the boat and was able to calibrate the compass with a 21 degree deviation. The boat is fiberglass and the factory install of the fluxgate compass is about 2' from the saildrive but last year the system worked fine. Despite calibrating the compass the autopilot did not hold a steady course. This has been the last time I have been able to calibrate the compass. Multiple attempts at swinging boat for prolonged periods of time fails to show any deviation reading. If I purposely spin the boat quickly the autopilot never reads "too fast". I performed a factory reset and it still will not calibrate. The deviation now reads zero after the reset , if I align the fluxgate compass to match the magnetic compass (compass not calibrated), the course is not steady. I moved the autopilot further from the engine and saildrive and other ferous metals which did not fix the problem. I used my multimeter to test the compass as a previous thread recommended, the readings were: red to green 4.5 ohms (expected 4), red to yellow 4.6 ohms (expected 4), green to yellow 8.0 ohms (expected 8) screen to blue 8.0 (expected 8), all other color combinations read OL. I moved the fluxgate compass to the cockpit and rotated by hand, 90 degree rotation changed the fluxgate reading 30 degrees, when rotated again 180 degrees, the fluxgate reading did not change despite rotation. I purchased a new fluxgate compass, did another factory reset and there was still was no calibration in both locations (near saildrive and distant from the saildrive, engine). Would appreciate your advice what to do next. I understand that Raymaraine will examine and fix older instruments, what is the cost of doing a diagnotic test, what are my options in regards to purchasing a new computer for the old system, new controller for the old system or entire new system? My chartplotter is a Raymarine E 80, Thank you in advance for your advice.