Compass calibration issue

[Two Truths]

I have a Simrad electronics package with the B&G Precision 9 solid-state compass (circa 2018). When the system is calibrated it works just fine, and the calibration process (rotating the boat) is simple and quick when you get used to it. Problem is, I find the boat has to be recalibrated every few days. That is, I will calibrate one day, and it holds the heading just fine. But a day or two later, when I turn the system back on, the heading and COG will diverge by up to 10 degrees or so (with no current or wind), and the divergence becomes obvious when I overlay the radar onto the chart. I can do a quick-fix using the calibration offset function, or rotate the boat again if conditions are good. But I wonder why it seems to lose its bearings when sitting unused. Anyone else have similar experiences? Ideas? Is this all my imagination?
(Note: I don't think local magnetic disturbance is an issue, since I turn the system off one day and the readings are accurate, and turn it on again a day or two later in the same location and the readings are off.)

 

[ScottRhodes13]

Are you making sure there is nothing magnetic (or iron) near the compass?

 

[kchace]

Also, there is a menu setting for the compass that allows it to autocalibrate basically anytime. That worked for me, but if its on, you may try turning that feature off.


Ken

 

[OldDan1943]

search around the flux gate for metal

 

[High Wire]

search around the flux gate for metal

Or untwisted DC supply wiring near the flux gate compass. Or DC single conductor, positive or negative, nearby. There are lots of those around your power distribution panel.

 

[Two Truths]

Thanks for all the suggestions. For some reason, auto-calibrate is not an option on my setup. The compass is mounted under the stairs to my forward berth, which places it 4 or 5 or so feet from the engine. (Is that close enough to have an effect?) And the only metal close to it is a small round metal cover (maybe 8" diameter) over a fiberglass holding tank. I'll check for other wiring nearby.

 

[Larry M]

Any audio speakers in the area? The magnet(s) in them can really affect a compass.

 

[ScottRhodes13]

Metal that is fixed in place should not be a problem -- calibration compensates for that as long as there is not too much. If there is too much it will indicate an error when calibrating.
The problem occurs when metal is placed close (within 1 or 2 feet in my experience) to the compass after it has been calibrated.

 

[mncruiser]

I have this same problem with my Raymarine 2018 era system and am also fighting to figure out the cause.

Same thing, my calibration process fixes it.

Same location for the compass, under the stairs heading forward on a 2001 Mainship 390.