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post #1 of 12 Old 08-10-2008 Thread Starter
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Autopilot when crazy

The other day I motor-sail solo tp an island 10 miles away to meet so,e friends for bbq and overnight. Next day as I motor back, my autopilot shows >+10deg offset from gps reading. No problem, I just set it and let it run but shortly the pilot behave crazy and started swinging the boat. I check and the pilot bearing swings all over the place. Switch it off and on again - no luck. So I continue on the journey, 1/2 hr later I put the pilot back to auto and presto! it works just fine for 1 hr then it acts up again. When this happens, I tried swinging the autopilot using the User Cal feature but it doesn't seems to help. Back at the dock the autopilot bearing looks to be normal. So what gives? I've Raymarine ST4000+ MKII Wheel with Rudder Ref Unit.

Ken
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post #2 of 12 Old 08-10-2008
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I'm no expert, but I would first check all the wiring related to the autopilot and make sure you're not getting a short anywhere.

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post #3 of 12 Old 08-10-2008
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I'd say that this is a problem with fluxgate compass. I would check its wiring first, and also whether there are any new metal objects nearby.
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post #4 of 12 Old 08-10-2008
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Quote:
Originally Posted by brak View Post
I'd say that this is a problem with fluxgate compass. I would check its wiring first, and also whether there are any new metal objects nearby.
Then do the recalibrate procedure
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post #5 of 12 Old 08-10-2008
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I think brak's suggestion merits looking at. Earlier this year on a trip in the Bahamas, we experienced similar behavior on a friend's catamaran after new crew members put the canned goods away. After scratching our heads for quite awhile we checked the cabinet where the flux compass is located only to find it buried under about a dozen steel canned goods. We removed the cans and didn't see the problem repeat for the rest of the trip.

I would also verify the the rudder position reference sensor is properly aligned. On our Chesapeake trip in May the autopilot on Whampoa began to act up and it would struggle to maintain a heading even in calm seas. We went over all the components carefully and found that the rudder position indicator arm was loose and had been bumped out of alignment during heavy weather. Aligning this and tightening things up resolved the problem and we continued the trip with no further problems with the autopilot.

I'm not sure how your system is set up but make sure nothing is physically interfering with the unit.

Good luck with the problem.

Regards, John

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post #6 of 12 Old 08-10-2008
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That happened to me, too. Motor-sailing along on autopilot, and we suddenly took an excursion.

My tool bag had made it's way across the sole and ended up next to the fluxgate compass. Moved the metal and all was OK.

I'm not saying that this was your problem, but it's something to think about.

Hud
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post #7 of 12 Old 08-10-2008
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Smile The likelyhood

Quote:
Originally Posted by trantor12020 View Post
The other day I motor-sail solo tp an island 10 miles away to meet so,e friends for bbq and overnight. Next day as I motor back, my autopilot shows >+10deg offset from gps reading. No problem, I just set it and let it run but shortly the pilot behave crazy and started swinging the boat. I check and the pilot bearing swings all over the place. Switch it off and on again - no luck. So I continue on the journey, 1/2 hr later I put the pilot back to auto and presto! it works just fine for 1 hr then it acts up again. When this happens, I tried swinging the autopilot using the User Cal feature but it doesn't seems to help. Back at the dock the autopilot bearing looks to be normal. So what gives? I've Raymarine ST4000+ MKII Wheel with Rudder Ref Unit.
Most likely you have a bad connection to your FLUXGATE COMPASS or something is stoved too close to it and makes it fluctuate on the heading.
Good luck keep smiling Capt Thor
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post #8 of 12 Old 08-10-2008
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BTW, there are a lot of things that have strong magnets in them that you might not think of. The emergency "shake" flashlights have strong permanent magnets in them. Check to make sure that there is nothing near the fluxgate compass.

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post #9 of 12 Old 08-10-2008 Thread Starter
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Thanks guys. Now what has changed, I've put a large SS pot in the galley cabinet (close to fluxgate) that didn't seems to affect the autopilot for the trip up. After trip the pot gets transferred to another boat so I doubt that's the cause as I've done the User Cal swing as mentioned. Connections - I have to check. Rudder Sensor - I have to check the mounting since it sits on a wooden puck. There has been pretty wet weather lately so the wooden puck could have been affected some. I sure hope its not the ST4000+ Display set failing. I won't be back to boat for next 2-3 weeks (on business trip), but will reverting with findings after that. Cheers.

Ken
2002 Hunter 326, SV Millennium 2
1999 Macgregor 26X, SV Millennium
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post #10 of 12 Old 08-10-2008
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The wiring, the fluxgate, and also RFI: Radio frequency interference getting into the wiring from the compass to the autopilot, or into the autopilot's main board. RFI can take strange forms, for instance, any GSM Palm Treo (Tmobile, AT&T, etc.) will create audio noises on any computer or car stereo, etc. within two feet of it, sometimes once a day sometimes once an hour, as the phone communicates with the local towers--when it is NOT being used.

Any new gadgets aboard the boat? Any radios or bluetooth-equipped devices?

The last possibility would be that the autopilot itself has gone mad, and something is wrong in the brains of it. Could literally be a loose screw or a strand of wire floating around in there, or a cold solder joint that was working open and closed. It is worth opening up and eyeballing it with a magnifier, to see if any of the joints look bad. Cold solder joints plague all kinds of gear.
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