Raymarine - Compass heading sudden change?

[Tim Good]

I have a Raymarine E80 and a fairly standard Raymarine flux gate compass down below. It has been fine for years and then just as we approached the Norwegian coast it suddenly decide to begin reading out by nearly 120 degrees.

I have tried the recalibration by turning in circles and tried setting the heading to match COG from the GPS but neither make any difference. Has anyone else had this problem?

 

[Sandyman]

Seem to recall coming across lots of magnetic anomalies when I was up there in the 70's.
Check to see if your hand held is giving a similar reading.

 

[duncan99210]

The symptoms described by the OP match ones I encountered. The fault lay in the wiring between the flux gate compass and the rest of the system. There was a loose connection in one of the wires. Remaking the connections solved the problem.

 

[Tim Good]

Seem to recall coming across lots of magnetic anomalies when I was up there in the 70's.
Check to see if your hand held is giving a similar reading.

Yes hand held is fine. That's how we knew it was out initially. Now travelled up 100 miles to Alesund and it's still out by a mile.

 

[Sandyman]

Yes hand held is fine. That's how we knew it was out initially. Now travelled up 100 miles to Alesund and it's still out by a mile.

I would look at what Duncan is suggesting. A lose connection or broken wire would put an error of around 120 degrees into the system.

 

[Tim Good]

I would look at what Duncan is suggesting. A lose connection or broken wire would put an error of around 120 degrees into the system.

I just went through all the connections from the compas through to the plotter and all seem fine. Removed and re plugged them. I can voucher for the integrity of the cables. Doubtful one would have just suddenly been compromised.

 

[pvb]

I just went through all the connections from the compas through to the plotter and all seem fine. Removed and re plugged them. I can voucher for the integrity of the cables. Doubtful one would have just suddenly been compromised.

There's a little ribbon cable inside the fluxgate which can fail.

 

[Stoshak]

Does it feed a Course Computer? Computer internals can effect output, esp if S1G.

 

[Tim Good]

Update:

Ok it's working. We're back on passage and the "align heading to COG" function now worked and brought it all back in line! Must have been a loose connection somewhere. Didn't determine which one it was as I just unplugged and cleaned each one.

All good now though! Thanks from Alesund!

 

[RobbieW]

If its the older sort with wire wound coils on a gimbal inside, bear in mind there are 3 coils 120 degrees apart. I've had one of those fail in the past, the resistance of one coil was very different to the other two and, iirc, the symptom was a 120 degree jump as the boat circled.