“Wonky” autopilot compass

[DougM]

I’m guessing age might have something to do with it, but my Raymarine ST6000 autopilot compass has evidently lost its mind... its on its 14th season.

The autopilot compass bearing reads anywhere from 90 to 180 degrees “off”from the magnetic compass, depending on the actual heading. I have done the calibration and it seemed to work for a day. The next time out, the problem recurred. Yesterday, on a constant heading the autopilot compass was fluctuating 60 to 180 degrees either side of the actual heading.

Nothing has changed as far as the boat. no wrenches next to the compass, no new additions to the boat itself, etc.

Installed a new Raymarine eSeries MFD 2 years ago, and it interfaced flawlessly all last year with the rest of the ST60 instruments and autopilot, so I’m assuming that is not the root cause.
Any suggestions would be appreciated.

 

[Ron20324]

Yesterday, on a constant heading the autopilot compass was fluctuating 60 to 180 degrees either side of the actual heading. Any suggestions would be appreciated.

You're not going by a bridge support or pier or something made with concrete that would have a metal form around it? The Academy bridge over the Severn River is like that. One gal said the fluctuations almost made her autopilot drive the boat into an adjacent footing. Now she knows better - "local knowledge".

 

[dlochner]

Have you tried to recalibrate the compass?

You might want to down load a magnetometer app and check the area around the compass for stray magnetic fields.

I used one from GEMECO for the iPhone, I assume there is also an android version.

 

[DougM]

You're not going by a bridge support or pier or something made with concrete that would have a metal form around it? The Academy bridge over the Severn River is like that. One gal said the fluctuations almost made her autopilot drive the boat into an adjacent footing. Now she knows better - "local knowledge".

Hey Ron,
There aren’t any bridges 3 or 4 miles off shore in Lake Michigan. If I find one out there, I’ll claim it and offer for sale to you dirt cheap...

 

[jviss]

Well, it's the fluxgate compass. Or, the connections from the fluxgate compass to the autopilot course computer.

I believe these have an internal gimbal mount, and if it breaks, will yield kooky results. Happened to a friend of mine.

 

[Tally Ho]

Have you tried swinging the compass a few times? Mine was wonky once, and all I did was take the boat out and make a few circles (3 I think) and all was well.

Greg

 

[SycloneDriver]

Mine acted like that on a unit I bought on ebay. It was supposed to be good working unit, right! I knew there was TSB on the Raymarine website that covered this issue. Some of the units had a very small surface mount capacitor installed backwards. Mine was one of the defective units. I can solder but I had never worked with surface mount components so I tried to find a shop to do the work, no luck. I did it myself and it has been working fine for about 3 years now.

 

[jviss]

capacitor installed backwards

Fascinating that a cap backwards would cause a problem. Was it an electrolytic, or perhaps tantalum? Did you have to replace it, or just reverse it?

 

[SycloneDriver]

I think it is tantalum.
The TSB said reinstall the original in the correct orientation, IIRC. I reused the original.
The hardest part was seeing the tiny thing. Turned on every light and had the wife shine a flashlight on it. Had to wear some reading glasses too. Three years later I need reading glasses just to type/read this.

 

[jviss]

Interesting, tantalums can explode if subjected to the wrong polarity DC.

 

[SycloneDriver]

Good thing it's tiny!

 

[jssailem]

Have you tried swinging the compass a few times?

I did that once.
Tied a rope to it and whipped it around above my head... Felt great.
Only issue was the rope came out of my hand and the sucker went sailing through the air. I was lucky. It landed on the beach and was all ok when I found it.
Never tried that again.