Autopilot only corrects in one direction - SailNet Community
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post #1 of 14 Old 12-23-2019 Thread Starter
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Autopilot only corrects in one direction

We have an Autohelm 4000 (non Raymarine, the black box). It worked fine last summer but now the boat will only correct to port. There is a brown and blue wire that power the motor. When I turn the control unit to the right, I get current across the two wires. When I turn it to the left, I get nothing. I get nothing in either direction if I attempt to press the +/- buttons. When I reverse the polarity switch on the back of the unit, it will correct to starboard but not to port.

Seems like a problem with the control unit, right? Any idea what could be bad or how to troubleshoot further? The compass device is on a gimbal but it appears to move freely in all directions.
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post #2 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

Look for magnetic things near the AP's compass.

pay attention... someone's life depends on it
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post #3 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

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Originally Posted by glossa View Post
We have an Autohelm 4000

They are significantly old and out of date, arn't they? It might be end of life. But I get the feeling the control head can be replaced without needing to replace the drive... the drive being the expensive bit.


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post #4 of 14 Old 12-24-2019 Thread Starter
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Re: Autopilot only corrects in one direction

I will check. I don't quite understand how the compass works; from what I can see, it doesn't have any moving parts except for the gimbal.
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post #5 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

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Originally Posted by glossa View Post
I will check. I don't quite understand how the compass works; from what I can see, it doesn't have any moving parts except for the gimbal.
any compass will show the wrong reading when a magnet is brought close. Things like magnetic flashlights can foul your compass.

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post #6 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

It won't be the compass. Most likely a failure in the power output circuitry in the controller. Probably the FET bank controlling that side of the reversible power output. Unless you can find someone who can do board-level repair, it will be cost effective to get a new controller.

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post #7 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

happened to us with our alpha 3000....cause was a metal container too close to the compass in a locker. Turns out you don't want any metal close, magnetized or not. Once we moved it everything worked fine.
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post #8 of 14 Old 12-24-2019
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Re: Autopilot only corrects in one direction

Likely bad solder connection(s) to one or more of the FET transistors (big black flat looking things).
If you or someone you know can solder, it's a relatively easy fix.
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post #9 of 14 Old 12-25-2019 Thread Starter
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Re: Autopilot only corrects in one direction

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Originally Posted by senormechanico View Post
Likely bad solder connection(s) to one or more of the FET transistors (big black flat looking things).
If you or someone you know can solder, it's a relatively easy fix.
Can the FETs be tested in place?

I also had to disconnect and reconnect the wires to the 4-pin connector to the control head, to replace the mounting block. The unit worked fine before I did this so I wonder if I fried some of the transistors, possibly re-connecting two of the wires wrong. Though the wires do seem to be in the right positions.
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post #10 of 14 Old 12-25-2019
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Re: Autopilot only corrects in one direction

Pull the connector and check to make sure none of the pins broke or bent.

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