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Old 04-11-2018, 12:42   #1
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ST4000 Autohelm Goes Starboard

I have an old ST4000 Mk1 wheel pilot. When I press Auto, the wheel slowly is commanded to starboard. If I press -10 deg, it will momentarily turn port, so I know the drive works in both directions. But then it will turn starboard until the off course alarm activates. I have moved anything metal away from the compass and tested the wires for resistance and they seem okay (blue to screen <10ohm, Red-yellow and Red to green <5ohm per spec). Anyone have their autohelm not keep course like this? I'm in the Caribbean, so north latitude shouldn't be an issue.... As for calibration, I can only seem to change the deviation in the compass which has no affect on the issue. I only have the manual for a mk2 and I don't get the list of different Cal values to change as described there.
Thanks for helping!!
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Old 04-11-2018, 13:10   #2
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Re: ST4000 Autohelm Goes Starboard

Does it do this all the time?

It sounds like the heading sensor is going out. Or there is something affecting the heading sensor. Are there any large power draws near the heading sensor? Are you close to power lines?
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Old 04-11-2018, 19:09   #3
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Re: ST4000 Autohelm Goes Starboard

Do you have the two wires going to the wheel drive swapped maybe?..I did that once and my drive did that..
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Old 04-11-2018, 20:12   #4
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Re: ST4000 Autohelm Goes Starboard

There have been threads about this.
I fixed my own ST50 and posted about it.
There are four power FET transistors in the head unit in a bridge configuration which feeds the drive motor.
Each one has three leads. Out of a total of twelve solder connections, eight or nine of those were bad.


Use a soldering pencil, rosin core solder, and you're done.


The symptom could be as you describe either port or starboard, or it might be sudden rudder change.
Then when the connection(s) come together, the autopilot slowly resumes course.
Mine was worse when it warmed up.
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Old 04-11-2018, 23:54   #5
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Re: ST4000 Autohelm Goes Starboard

Quote:
Originally Posted by senormechanico View Post
There have been threads about this.
I fixed my own ST50 and posted about it.
There are four power FET transistors in the head unit in a bridge configuration which feeds the drive motor.
Each one has three leads. Out of a total of twelve solder connections, eight or nine of those were bad.


Use a soldering pencil, rosin core solder, and you're done.


The symptom could be as you describe either port or starboard, or it might be sudden rudder change.
Then when the connection(s) come together, the autopilot slowly resumes course.
Mine was worse when it warmed up.
Zstine says he can make it turn both ways by pressing the -10
button thereby indicating that the H bridge is working. However he did not say that it worked the opposite when pressing the +10 button only that it turned itself this way.

My ST4000 exhibited similar symptoms after a nearby lightening strike corrupted it's memory. This can be fixed by going into dealer setup and telling it it is a different model. On going out of dealer setup it loads the program for the new model over the corrupted program. Then you go back into dealer setup and re-instruct it to the correct model which will load when you go out of dealer setup again again.
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Old 05-11-2018, 09:51   #6
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Re: ST4000 Autohelm Goes Starboard

Check your rudder position indicator. If it sticks or is intermittent your will have these same symptoms. Much easier to fix than other things. It is a simple rheostat
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Old 05-11-2018, 20:11   #7
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Re: ST4000 Autohelm Goes Starboard

Had a friend with similar problems I said it seemed that there was close to metal or something magnetized! That when his wife listening to our conversation said she stored her exercises magnets under the aft birth mattress! Problem solved!!
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Old 07-11-2018, 21:42   #8
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Re: ST4000 Autohelm Goes Starboard

Increase the ballast on the port side. It will balance out.
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