Raymarine Autopilot getting "lost"

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Falling Star

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My ST6002 works fine, then seems to lose the heading. Occasionally it will be wrong from initial power on.

It can go 50 to 100 degrees out from the real heading. i.e. Steering compass and chartplotter indicate, say, 180. Autopilot indicates 115 or 260.

I have had a look near the fluxgate and can't see anything that would affect it.

All ideas welcome. Thanks
 
Something magnetic near the fluxgate???

Over the years I've had several items, which the crew didn't realise would be magnetic, cause all sorts of problems the the Raymarine fluxgate,

Tinned food, a cake time, biscuit tin, and the lifting keel on the southerly which cause a massive shift in the flux gate when raised. These have often been stowed in a locker close to the fluxgate by members of the crew not realising where the fluxgate was fitted or that they may be magnetic.
 
Step 0: Check again, any metal within 1.5m can easily mess with the compass, further if it is magnetized. I cringe a bit when I see people gleefully replacing their hooked door latches with magnetic ones from B&Q. In my case it was coat hangers with a wire hook - swapped out for plastic cast coat hangers and compass happy. Electromagnetic fields also mess with the compass, so switch off everything but the instruments and see if your compass still goes haywire. Cheap 12V USB chargers are often not shielded at all.

Step 1: Do the calibration dance with your boat, see instruction manual. Note that with compasses on boats, just because it is spot on pointing one way doesn't mean it will also be spot on when pointed in another direction, so therefore the dance involves driving the boat in a circle.

Step 2: Check wiring from the fluxgate to processor box - any lose wires may be causing this, although normally this should be reported as fault.

Step 3: Either your fluxgate or worse, processor box is knackered. Beg/borrow/steal a replacement fluxgate (occasionally seen on eBay under £100) and try that.
 
Could be rudder sensor. These are just a potentiometer (variable resistor) & are a "wear" item-especially near center rudder position.
Bring up the "rudder angle meter " display in Stby. Manually move rudder hard to hard very slowly with wheel/tiller.Look for jumpiness in angle display.
Check the sender linkage for wear also.
 
If you can display the fluxgate heading somewhere (e.g. on chartplotter) that is the easiest way to see if it is sending good data. Just watch it for a while on a variety of headings.
 
Len Ingalls said:
Could be rudder sensor.
Click to expand...

They're also easy even to test with a meter. This is for mine, and I don't think they've changed much over the years:

Looking at your display watch the rudder bar indicator and move the rudder. Does it move as it should?
Does the rudder indicator wobble/move not as it should? If it does it indicates that the rudder reference unit is malfunctioning.
Disconnect from the course computer and then Using a Multimeter check the following,
Cable colour ---- Arm position ----- Resistance
Green/Red ---- Any position ----- 5k ohm +/- 5%
Blue/Green ----- Anti clockwise stop ---- 1.66k ohm +/- 10%
Blue/Green ---- Clockwise stop ----- 3.3k ohm +/- 10%
 
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