Autohelm system - Heading Error?

[Tim Good]

Hello. The other day the small boat icon on my Raymarine E80 started facing an odd direction. It was facing the direction relative to the wind rather than its actual heading. The COG line was accurate but the heading wrong. The angle of the wind to boat icon was accurate but as the boat icon was facing the wrong way then the wind arrow was also wrong. Autopilot still worked and so did wind angle relative to the boat. Have a look at the images below. What do you think is cause of the error?

Note that in this case we were going 171T and the wind was dead astern but the autopilot thinks were going 285 and so the wind arrow is plotted wrongly but correct, relative to the boat icon.

Perhaps these images might help:

 

[laika]

Oops no. I'll reinstate my comment as second look at that display shows what I thought first time round. Heading is off. Has someone stacked something metal in the locker where the fluxgate compass lives? The displayed wind angle will be relative to heading, so if heading is off so will wind angle be (but correct relative to boat). I've seen this happen when someone has provisioned heartily and shoved a load of cans up next to the compass.

 

[Tim Good]

I've seen this happen when someone has provisioned heartily and shoved a load of cans up next to the compass.

The compass is located right down under the floorboards in its own compartment. Nothing is in the locker nor has anything changed. It checked it was still mounted ok and its connections ok into the little control box but all appeared to be sound.

 

[laika]

Nothing is in the locker nor has anything changed. It checked it was still mounted ok and its connections ok into the little control box but all appeared to be sound.

Well it was worth suggesting. If this were my boat I'd still be thinking "compass issue" and probably be reaching for a multimeter and google. Your compass may be different but this turned up while reaching for google:
http://forum.raymarine.com/showthread.php?tid=96

Edit: you'll doubtless already follow my thinking but to state the obvious...the course computer will be working out heading from the compass input and then punting heading out onto the seatalk bus where it's displayed by the control head and the used by the E80 for plotting. There's no problem with the E80: it's only using what is obviously being put onto the seatalk bus so the issue is either with the course computer, the compass or the wiring between them. You've discounted the wiring. My money would be on the compass.

 

[Tim Good]

Well it was worth suggesting. If this were my boat I'd still be thinking "compass issue" and probably be reaching for a multimeter and google. Your compass may be different but this turned up while reaching for google:
http://forum.raymarine.com/showthread.php?tid=96

Thanks! I'll get on it.

 

[ithet]

To add to what Laika said, your E80 is showing COG as measured from GPS position changes, this seems correct. You could edit the E80 status bar to show heading taken from the fluxgate, but this is already shown on the ST7000.

Does the heading reading (as on the ST7000 in standby) ever change from 285? You could first try unmounting the fluxgate and slowly rotating while observing the ST7000 display. As well a connection problem, It is also possible that the fluxgate compass has come off it's gimbal (internally I'm afraid). There is info on web on how to correct this.

 

[duncan99210]

I’ve had this sort of error occur with my setup: it was down to the connections between the compass and the course computer. Remaking the connections revealed a couple of poor crimps being the cause.

 

[Tim Good]

I’ve had this sort of error occur with my setup: it was down to the connections between the compass and the course computer. Remaking the connections revealed a couple of poor crimps being the cause.

Thanks. I’ll go through and redo the connections prior to fiddling with the compass.