Erratic autopilot compass headings - SailNet Community

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Old 05-30-2007
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Erratic autopilot compass headings

I have a raymarine ST linear drive autopilot system with a fluxgate compass with gyro. It worked flawlessly for 2500+nm Then it was put up on the hard for 1 1/2yrs. (2 winters in the NorthEast)

Now when trying to get things going again the compass is erratic. Sometimes off by 100 degress or more. I can't complete the "swing ship." In the seatrial display is just stays on the "Turn Boat" screen.

Any Ideas.

I found this on Raymarine.. Which I find to be a poor response to the question. Given it Worked GREAT. Nothing Changed. Except Time and potential water/freezing issues. I don't think it's a location issue.


Erratic autopilot compass headings

My autopilot compass is very erratic. IT was working fine, but now it is all over the place. What might be wrong?
There could be something interfering with your fluxgate compass.

The correct positioning of the fluxgate compass is crucial if ultimate
performance is to be achieved. To minimize gimbal disturbance, the fluxgate should ideally be positioned as near as possible to the pitch and roll center of the vessel.

Make sure the fluxgate compass is located on a suitable vertical surface. The fluxgate should be positioned at least 2ft. 6in. (0.8m) away from the vessel's steering compass in order to avoid deviation of both compasses. To avoid compass deviation and reduction in sensitivity of the sensor, the fluxgate must also be positioned at least 3ft. away from iron objects, ( engine, keel, loudspeakers), as well as other electrical devices such as batteries, AC sources, chargers, speakers, audio equipment etc..

If any doubt exists over magnetic suitability of the chosen site, the position may be surveyed using a hand bearing compass. The hand bearing compass should be fixed in the chosen position and the vessel swung through 360 degrees. Relative differences in reading between the hand bearing compass and the vessel's main steering compass should, ideally, not exceed 10 degrees on any heading.

Temporarily mount the compass sensor in the desired location, if the deviation correction during your seatrials exceeds 15 degrees, then you need to find a better location for the compass sensor.

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Old 05-30-2007
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see if problem is with fluxgate or display unit. 1.set autopilot to steer by Wind angle. see if it work. 2.remove fluxgate and shake it see if there any movement inside (or jammed). 3.borrow fluxgate/display for test.
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