PG700 Heading Deviation to Magnetic Compass

[AvalonGB]

This issue has just recently started happening. Installation has not changed nor have we installed new equipment. TZT14s, NAVPiolt711, and PG700 installed 8 years ago and all has worked fine until last few days.

We've been running the boat in the FL keys and up FL coast for the last few days. At the start of the typical 9 hour run all is fine, heading from Auto pilot and compass align within a few degrees. After 3 or so hours all of a sudden there is an approximate 30 degree variance between heading on NavPilot and magnetic COG. I've rebooted system while underway but no change. The next day issue repeats, all is aligned between autopilot / heading and magnetic COG until 3 hours into run when approximate 30 degree variance all of a sudden reappears.

Any ideas what is going wrong? What steps should I take to trouble shoot?

Thanks,
Tim

 

[Johnny Electron]

It sounds like something new was added to the boat that is pulling the compass when the item is turned on. It can also be metal or magnets that are placed in the area. One example I can think of is motorized fishing reels. If placed in the area where the compass is; it will be a problem for your heading. That is just one example. If something turning on like toilet upflush motor, you should be able to go to the boat and run only the pilot and test, while turning on items and switches until you find the interference.