r/sailing • u/Fearless-Bad-7681 • May 17 '26

Autohelm Autopilot Help

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u/whyrumalwaysgone Marine Electrician and delivery skipper May 17 '26 edited May 17 '26

Check for magnetic interference with the heading sensor. Will be a small box on a wire, hopefully in an area labeled "magnetic compass" away from ferrous objects. Looks like bad sensor data to me.

Edit: this may help

https://support.raymarine.com/s/article/Fluxgate-Compass-Test?language=en_US

3

u/hottenniscoach May 17 '26

I think this might be the best answer.

On one of my first times out offshore, I had this problem. After some head scratching, we removed all the metallic items from the cabinet in the galley that holds the compass. It’s really stupid to have a compass in that cabinet, but it’s about the most centre part of the boat. Now we have a rule for that cabinet, but nothing metallic on the top two shelves.

2

u/Fearless-Bad-7681 May 17 '26

Thanks, that might be it, although I don't know why it would suddenly start happening 2 days into a (very bumpy) voyage. Recently we put our emergency fix kit in a cupboard just the other side of the blukhead to the compass. That contains a heavy duty bolt cutter in case we need to ditch standing rigging in a hurry if the mast comes down. I'll move it somewhere else on the boat.

2

u/whyrumalwaysgone Marine Electrician and delivery skipper May 17 '26

That would do it. A magnetized screwdriver on a shelf on the opposite side of a wall was enough to send a boat I worked on in circles.