Can Someone Please Explain to Me . . .

[barnakiel]

1) check connections - sometimes the wires get worn at the box,
2) any new equipment added recently? - interference possible,
3) check the sensor (e-mail Raymarine for instructions - resistance is measured),
4) use your neighbour's sensor, if it works fine, yours is busted.

For those who get weird readings - make sure you have been thru full calibration of the autopilot. This is important. Not only the circles but also the alignment correction. Re-calibrate, in necessary. Unfortunately, these sensors do break down at times.

b.

[Dockhead]

Originally Posted by barnakiel

1) check connections - sometimes the wires get worn at the box,
2) any new equipment added recently? - interference possible,
3) check the sensor (e-mail Raymarine for instructions - resistance is measured),
4) use your neighbour's sensor, if it works fine, yours is busted.

For those who get weird readings - make sure you have been thru full calibration of the autopilot. This is important. Not only the circles but also the alignment correction. Re-calibrate, in necessary. Unfortunately, these sensors do break down at times.

b.

OK, thanks, but our autopilot works perfectly. My real puzzle is how could the autopilot be getting good heading data when the radar/plotter does not. It doesn't make any sense to me. They're all on one network as far as I understand. Or?

[fishwife]

Your autopilot may be taking it's heading from the GPS so that's possibly a red herring. It seems more and more likely that the gyro may be at fault. Sorry I can't be more helpful.

P.

[Dreaming Yachtsman]

Dockhead,

I have been trying to fix a similar problem on my system (Raymarine autopilot, Furuno radar/chartplotter) and have come to the conclusion that it is an input/output problem on the radar unit, which is now at the factory awaiting repair. Autopilot works fine sending correct heading information throughout the system but the radar/chartplotter remains in "Heads up" mode. Also, the chartplotter is not sending correct position output to my Skymate and VHF. On occasion, the "Lost GPS input" alarm sounds on the chartplotter, really giving me a fit. Hopefully the factory tech will call me soon so she can find and fix the problem.

[barnakiel]

Originally Posted by Dockhead

OK, thanks, but our autopilot works perfectly. My real puzzle is how could the autopilot be getting good heading data when the radar/plotter does not. It doesn't make any sense to me. They're all on one network as far as I understand. Or?

You are jumping to conclusions when you think the autopilot is getting good heading data (while the radar (apparently) does not). What is certain, the radar shows erratic info while the autopilot seems to be doing just fine.

Possible reasons, non-exclusive list:

- autopilot does data processing fine, radar does not (software problems or hardware problems),
- one of the above using compass data while the other using data from another source,
- differences in set-up mask erratic data (e.g. by the use of averaging filter),
etc..

Depending on your autopilot unit, you may be able to tune the averaging to the allowed minimum and check the readout in standby. Another thing one can do is unplug the compass from the unit and plug it in at another point (network bus or the other instrument).

Again, make sure the cabling is fine (shorten the cables and plug in freshly stripped cores), make sure the compass is fine (by doing the tests as per Raymarine instruction) and by observing the compass readout on compass (or autopilot) instrument with tuned down averaging.

Go piece by piece, starting with the most obvious: connections, cables, the sensor, and so on. One element at a time, and you will find the bug.

PS You do not have to take the boat out for tests - just dismount the compass sensor and turn it by hand).

b.

[Dockhead]

Thanks, everyone, most useful. I'll have another go at it next time I'm on the boat.