Autopilot literally spinning ..

[crankysailor]

So as some of you might have read on another thread, I recently had an incident where a 6-7 bft. wind caught us by surprise at night when only 2-3 were forecasted. I was on autopilot (Navman brand, probably installed by prev. owner around 2006) and on a beam reach with almost full sails (one reef in the main, full genoa) we got flattened. The autopilot started beeping like mad which I had never heard it doing and it just added to the confusion of the moment. I sprang up and disabled it and took manual control of the boat and the rest.. well.. different topic

After sorting out the mess and wanting to continue the passage two days later, we sailed out and turned on the autopilot .. it sailed straight for a bit and then it started turning. I thought something had caught the rudder or something! I regained control of the boat and scratched my head... ok.. try again.. same deal.. autopilot just goes straight for a few moments and then it spins like mad. Great.. handsteering 14 hours with two of us it is then.. great

I noticed the magnetic heading on the display is about 100 degrees off.. I would have thought that the forces during the incident we had would have caused some damage to the actuator or something else of a mechanical nature. But in fact, the turning left and right part seems ok. It seems it is something either with the brains or the magnetic compass .. but why would any of these go berserk just cause we had too much pressure on the sails??

We tried factory reset but when I tried calibrating it, one is supposed to do 2 1/2 turns slowly with the boat.. the display suggests there is an area of about 100 degrees where the autopilot says I am not turning.. but I am ofc. Hmm...

Ideas, suggestions? maybe it is in fact unrelated to the incident and the failure is a coincidence?.. thx!

[pcmm]

When you got flattened, did anything ferrous end up against the compass sensor?

[crankysailor]

I did check that and didn't see anything.....

... wait.. would a lithium ion battery (from an e-scooter kind of monowheel I use to get around interfere with it? damn it I think that is under the salon table and the compass is behind a wooden board next to it now that I think about it.. hmm... now I am not sure and the boat is on the hard for repairs and I am away. Crossing my fingers it is something that silly...

[goboatingnow]

Sounds like the flux gate compass is being interferes with all right.

[marcjsmith]

Since you got knocked down, is it possible the flux gate compass got damaged?

[crankysailor]

Originally Posted by marcjsmith

Since you got knocked down, is it possible the flux gate compass got damaged?

Well but that is the question.. can that be the cause? would overpowering the rig suddenly cause a feedback current thru the compass as to get it damaged? I would expect a problem with the actuator but not with the electronics of it..

[rslifkin]

Originally Posted by crankysailor

Well but that is the question.. can that be the cause? would overpowering the rig suddenly cause a feedback current thru the compass as to get it damaged? I would expect a problem with the actuator but not with the electronics of it..

It shouldn't, but if something got whacked against it in the knockdown it could cause damage.

[Sivaa]

In manual mode , if heading indication is satisfactory - heading sensor is still good .

In autopilot mode , choosing course direction in port & stbd side - gives one side turning response ? For your clarification , please .

[goboatingnow]

Before you do anything I suggest you rerun the AP setup and calibrate routines.

When I installed an new EV1 AP thd heading was perfect , engaging the AP caused dramatic turns.

Then I ran the calibration and setup process. Hey presto proper handling

[Sivaa]

Will it mean that heading is always 100° offset w.r.to bow ? Calibration or realignment of heading sensor to the boat's heading - difficult ?

[Brian.D]

I didn't see this, but I wonder if you were to totally disconnect power to the flux compass sensor for a couple of hours so as to do a literal reset. Turn off and on might not be the right thing since there may be a capacitor acting like a battery that is keeping internal settings. JMHO

Just out of curiosity, is the 100° variant to port (-100°) or to starboard (+100°) or, it is just plain off by 100°? And, if you set the course by adding or subtracting the 100° will the AP keep the correct heading?

[goboatingnow]

Again perform the complete recalibration of the system treating it like a new install.

Until that’s done forget trying to interpret things. If that doesn’t work something has failed