On my 52' steel monohull sailboat with an e7D chartplotter and all ST60+ and P70 instruments, I have never been able to get the Raymarine Fluxgate compass to provide reliable data to the autopilot.  Quite understandable I suppose on this steel boat in spit of raising the fluxgate up about 2m from the deck.

I recently installed an Airmar PB200 "Weather Station" at the top of the mast and did so in large part to be able to use the PB200 heading info to hopefully resolve my problems with the Fluxgate compass.  We are preparing to make the passage from here in Fiji back to Vancouver or Seattle and are therefore VERY anxious to have a rock solid autopilot and heading data.

My question is how to best connect the Airmar PB200 to the overall boat network and more specifically how to replace the Fluxgate heading data going to the S3 Autopilot and the P70 control head? 

Is it recommended that I disconnect the Fluxgate from the S3 entirely? 

How do I tell/set the S3 Autopilot to use the heading data from the PB200 and NOT the fluxgate compass?

Thank you VERY much for your assistance with this vexing problem.

Wayne & Christine Hodgins

s/v Learnativity

Vuda Pt. Marina, Fiji

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Sorry for the delay in response.

With the Weather station high on the mast, please be aware that the heading will swing wildly when the vessel is heeling.  With a steel hull you would have to move the fluxgate compass above the hull but you want to place the fluxgate high enough to be no affected by the hull but low enough not to swing wildly when the boat heels. 

The S3 course computer looks for heading data in this priority Fluxgate/NMEA 0183/Seatalk. If you are interested in bringing the PB200 into the system for heading.  You would disconnect the fluxgate from the S3 course computer and you would bring the PB200 into the NMEA 0183 interface on the course computer.  If the PB200 is a NMEA 2000 device you would need to convert the data from NMEA 2000 to NMEA 0183.  You can do that using a converter, there is a company called Actisense that manufactures a N2K to NMEA 0183 converter, called th...

I will recommend working on getting the fluxgate compass to work properly with the S3 course computer.  I have enclosed the compass test below to confirm a good working compass.  I have also enclosed a mounting instruction sheet of the compass location.  You can focus on the Steel Hull illustration.

Compass Test:

Multi-meter should be set to:

(a) Resistance scale

(b) 200 ohm scale

The following procedure should then be followed:

1. Disconnect the transducer from the system.

2. Connect one multi-meter lead to the red wire and the other lead to the green wire and a reading as indicated in the test data table should be present.

3. Follow the above procedure for all the color combinations indicated in the test data table.

4. If all readings match those indicated assume the compass transducer is functioning correctly.


Compass Test Data:


Red to Green - 4 ohms

Red to Yellow - 4 ohms

Green to Yellow - 8 ohms

Screen to Blue - 8 ohms

All other combinations - OPEN

You are looking for a short or open. A +or - 2 Ohm reading is allowed.

If this check indicates a fault with the compass then you will be best served by replacing the compass. If no problem is indicated then you should send the compass and the course computer to a repair facility for evaluation.


So pleased to get this response, thanks very much.  I've spent several years now trying my best to find some way to make the fluxgate work reliably and have concluded that it is just not possible on this boat.  I don't think it is so much a fault of the fluxgate as that it simply can't work and overcome the influence of all out steel.  It is a very big heavy all steel boat, 52' motorsailor and I have moved the fluxgate to quite a few different locations and none seem to work well at all.  It ends up being very high up off the pitch and roll centers which they don't like and it is VERY senstiive to the least bit of magnetic influence from as far away as 35 feet.  We can't use any computer equipment, phone or tablet chargers or the heading goes wild going round and round full 360 so the boat goes with it on AP.  We know about it now so know to be on guard all the time but clearly this is not satisfactory and down right dangerous to us as we are full time world cruisers and do some very long 3+ week passages quite regularly so we very much depend upon our autopilot so this has been a very serious problem for us.

The Airmar PB200 works extremely well actually and with this relatively new model it has 3 axis accellerometers in it that cancel out even the wildest of movements way up at the top of our mast.  There are a growing number of people on large sailboats using this PB200 for very effective autopilot heading and also super accurate wind data when we set the AP to wind model and so I am very optimisitc that the heading info the PB200 is putting out will breathe new life into our S3 autopilot.  Some excellent first hand reports from some very smart sailors over on Panbo.com discussion forums from the past 3 years or so that make for good reading and info if you or others are interested.

I very much appreciate the detailed instructions on how to disconnect the fluxgate and provide the PB200 heading data via the NMEA0183 inputs on the course computer.  Very disapointing that this cannot work directly with NMEA2000 but I have other 0183 data being generated and displayed so I'll figure out the best way to convert the NMEA2k strings from the PB200 to NMEA0183 and get that connected up to the course computer and see how it works.  

I had a heck of a time getting my previous new discussion topics postings to be "approved" for some reason so thanks again VERY much for getting back to me with this very helpful response.  


Anytime, contact us with further questions.

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