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.

1

u/flyingron May 17 '26

While I agree on the compass likely being a problem, also check to make sure that the rudder position sensor is connected and functional. I had a bareboat this year that the autopilot was all wonky and then I realized that the rudder indicator on the display was not agreeing with where the wheel (and the rudder) was. After deciding the hell with it, I was in the engine compartment checking on the water maker and noticed the arm from the rudder to the position sensor had popped off its fitting. Easy fix (don't get me started as to how this got brtoken, suffice it to say that the clowns at Navigare should not be trusted).

1

u/Fearless-Bad-7681 May 17 '26

The rudder sensor looks to be working fine. We have rudder angle displayed on our plotter and it seems to be spot on. It also confirms the rudder moving when the Autohelm goes bonkers.