Raymarine ST60 fluxgate compass suddenly going mad....

[jwilson]

This morning whilst motoring on autopilot the boat suddenly made a violent course deviation - about 90 degrees. After disenaging autopilot and correcting course I put it back on autopilot and it carried on OK, except that the electronic compass was showing about 90 degrees out from the actual course. Normally it is within a few degrees. No-one else on board so no-one suddenly putting anything magnetic near the fluxgate - wherever it is. It's one of the few bits on the boat (Jeanneau SO35) I've never actually found - I may have to follow wires from the ST6002 head.

This afternoon on the way back to the mooring the same thing happened - sudden 85 degree course alteration. I also noted that the B&G plotter was showing the little boat icon pointing about 90 degrees off the actual COG. This time I turned off all the electronics and turned them on again, and the fluxgate display was correct again and the boat icon was pointing the right way. The system is 2005 vintage Raymarine ST60s, feeding data to a modern B&G plotter via a Raymarine ST-STnG converter.

Anyone else had something similar happen? Anything other than the fluxgate could cause it?

 

[Stewproud]

This morning whilst motoring on autopilot the boat suddenly made a violent course deviation - about 90 degrees. After disenaging autopilot and correcting course I put it back on autopilot and it carried on OK, except that the electronic compass was showing about 90 degrees out from the actual course. Normally it is within a few degrees. No-one else on board so no-one suddenly putting anything magnetic near the fluxgate - wherever it is. It's one of the few bits on the boat (Jeanneau SO35) I've never actually found - I may have to follow wires from the ST6002 head.

This afternoon on the way back to the mooring the same thing happened - sudden 85 degree course alteration. I also noted that the B&G plotter was showing the little boat icon pointing about 90 degrees off the actual COG. This time I turned off all the electronics and turned them on again, and the fluxgate display was correct again and the boat icon was pointing the right way. The system is 2005 vintage Raymarine ST60s, feeding data to a modern B&G plotter via a Raymarine ST-STnG converter.

Anyone else had something similar happen? Anything other than the fluxgate could cause it?

I had a similar issue with an old Simrad system. The fluxgate sensor fed heading data via NMEA0183 to the AP300 autopilot computer, which then fen NMEA dat to the compass display and plotter. The fault was a card in the autopilot computer. I am not familiar with Raymarine ST60, but if the compass fluxgate uses NMEA2000 (Raymarine ST-STnG is NMEA2000) to talk to the system, then the fault will be in the fluxgate.
Best regards .. Stew

 

[rotrax]

One of the coils in the fluxgate compass is the likely culprit.

AFAIK they are available as spare parts.

We had ours replaced four years ago in Dartmouth by a local independant specialist.

He took the defective one which he said he would repair later, fitted a used but working one for what I considered a modest fee.

 

[Scotsailor]

I’ve experienced exactly this … and then I realised that my iPhone was nearby. … keep my iPhone well away now and it’s never happened since. That’s five years now.