Originally Posted by seadogmike
If you suspect that your autopilot is getting interference, you can check any power cables that are located near it for interference. There is an Ap that you can download for free to an android phone (i'm sure there is something similar for the I-phones as well). It is called a gauss meter. I have one on my phone that I use in cases like this. I don't know if it is related to the Tach issue, but I would suspect not. Probably 2 different gremlins. sometimes just moving a power cable closer to the autopilot cables can cause the issue.
Interesting. I will see if I can find that app for the iPhone. I did find some bungees with metal ends that were thrown on top of the flux compass and removed those. Have not had a chance to go out and retest/recalibrate the AP.
When the AP started acting up I tried to do a recalibration by doing the slow circle thing with the "swing compass" on, but too many boats to contend with and too many people on board for me to concentrate, so I couldn't finish that.
Think I got the Tach issue, but like the suggestion for an additional ground for the tach.