ST4000 - circles to starboard

[dmksails]

My boat came with a Raymarine ST4000 autopilot. I put the pilot into Auto mode and the boat then proceeds to turn hard to starboard. I've let it stay this way thru 2 complete circles.

I've tried a full reset to factory settings with no results. Now I'm trying to narrow the fault down to either the control unit or a sensor. Does anyone know of troubleshooting steps for that?

[senormechanico]

A very likely result of loose connections on the FET driver transistors (four of them) in the control head.
Each transistor has three leads. On mine, there were 8 bad connections out of 12 possible.
If you aren't great at soldering, leave it to someone who is.

[DeepFrz]

I could be the wires to the pump motor have been reversed.

[dmksails]

Thanks for the pointer to check the circuit boards.

My first job was creating test programs for the circuit boards use in sonar systems - I should have thought of that!

[Sylvaingagne]

inversion on drive electric feed
check polarity

[sailon46]

If everything connection wise checks out ok then try the obvious tell the controller which side of the boat you mounted it if its backwards youll be doing willies out there.

[compdoc]

check for magnetic interference near the control unit. In my case cockpit speaker magnets were the culprit. I removed the speakers and problem solved

[svfinlandia]

I upgraded my chart plotter from a C90W to a e97. The auto pilot work perfectly on the C90W but once e97 was installed and I would either initiate the track or a goto the boat with immediately Veer to the right for a while then back to the left for a while, then finally find the correct route and would be fine from there. So far I am living with it since there's lots of room ion the ocean but I am careful not to set a track or go to on the ICW.

Al, S/V Finlandia

[peter loveridge]

had similar thing on my ST4000 tiller pilot. Would happen usually after being fine for hours. Eventually I found the screen was not grounded. I fixed this and it's been ok ever since