On Tugly I experienced the same thing except it was right turns. My AP is a
Autohelm 6000 which has operated flawlessly for a few years except for the
sudden right turns. I noticed that the more beers my guests drank the more
unwanted turns were made. It seems that every time the fridge door was
opened the magnetic strip on the door would come within inches of the
fluxgate. No I haven't moved the fluxgate, I got rid of my friends. Easy
solution.

Bob Owens
TUGLY 26' Nordic Tug

As some of you may recall there was an incident  involving a large cruise
ship  in BC waters which also experienced  a sudden  uncommanded turn while
under autopilot  control.

This phenomenon  is by no means  uncommon. More so  in  recreational craft
where installations are done without  inspections and approvlas by  any
knowledgeable authority.

As Morley found out it could be something as simple as the magnetic stripe
on the fridge door, or the  automatic  power up from an inverter or other
large  current device. To that we now add  cell phones,  Blue Tooth
technology, wireless mice for  navigation computer use  and the list goes on.

Until a  major disaster  takes place whioch gets highlighted in the news;
no one is going to  do a complete investigation into the causes and effects
as I have  mentioned above.

It  is therefore incumbent on each  owner to become as aware as possible of
potential pitfalls in their own  boat.

Cheers

Arild