[CA] [CA11] Uncommanded 360 while in track mode

[hynespa]

While on a trip back from Catalina Island this weekend, I had the autopilot engaged in track mode, while I was navigating to a waypoint about 38 miles away.

Three times during the trip (all during the first 30 minutes of a 2.5 hour trip) the autopilot threw the rudder hard to port causing the boat to make a counterclockwise 360 loop while at cruising speed (14-15 kts).

This happened to me on a previous voyage back in May while the autopilot was in track mode following a route made up of multiple waypoints. That time I immediately put the autopilot in "Standby" mode and took control of the steering.

This time I let it go because I was in open water with no other boat traffic and I was curious if it would have the boat continue to do 360's. It only did one complete 360 before the autopilot automatically resumed course.

During the beginning of the uncommanded 360 the autopilot indicator showed the rudder hard to port. Then as the 360 continued the autopilot display changed to only showing "off course". As the 360 concluded it showed me back on course to the waypoint. The three different 360's I experienced were all in the first 30 minutes of the trip ... and were spaced about 5-8 minutes apart from each other... and they were all to port. After the last one the autopilot successfully navigated me to the waypoint in track mode over the next 1 1/2 hours without any more 360's.

I have attached a PDF diagram showing how my autopilot is wired to the MFD. I have the following:

* Raymarine S3G Course Computer
* Raymarine P70R Autopilot Controller
* Raymarine eS127 MFD

NOTE: The heading displayed on the autopilot controller is almost always 15-20 degrees off from the heading displayed on the MFD. I have gone through the autopilot calibration steps outlined in the P70R manual (e.g. the steps that involved driving the boat in slow circles) but the course displayed on the controller still doesn't match the course displayed on the MFD ... or soon goes back out of sync.

Happy to provide you any diagnostic information / logs / etc from the MFD if that would be helpful? You will just have to provide me instructions on how to generate / export these. Please let me know any other troubleshooting steps, etc. Thanks!!

[Chuck - Raymarine - Moderator]

Welcome back to the Raymarine Forum hynespa,

The reported symptom would typically be indicative of
- introduction of a magnetic field in the area of the fluxgate compass ... inspect the area around the fluxgate compass for sources of magnetism, particularly nearby electrical devices which may switch on / off automatically.

- a problem with the autopilot's gyro ... unplug the gyro's cable from the autopilot course computer's processor board. Unfortunately, replacement gyros are no longer available for the S1G/S2G/S3G autopilot course computers. The autopilot will no longer be gyro assisted autopilot and will accordingly function as a S3 autopilot course computer.

- with the fluxgate compass ... the fluxgate compass test should be performed and replaced if binding is detected or resistance measurements are not consistent with those specified within the fluxgate compass test

[hynespa]

I appreciate your response Chuck. A couple follow up questions:

a) I am not sure what the Fluxgate compass looks like. The one on my boat would be the original one installed with the S3G course computer when the boat was built in 2005. Is there a link to a photo of the 2005 Raymarine fluxgate compass, so that I can correctly identify it when I go searching in the boat for it?

b) Is there a photo or diagram showing where the gyro is plugged into on a S3G course computer board or step by step instructions on opening the S3G and unplugging the fluxgate?

c) I have attached a copy of the Raymarine S3G installation / wiring diagram. In the Fluxgate compass test it says to unplug the transducer and connect the multimeter to combinations of the Red/Green/Yellow/Blue wires. I don't see where the transducer is wired into the S3G - so I want to make sure I'm unplugging the right thing. Could you point out where it is wired into the S3G?

Thanks!

[Chuck - Raymarine - Moderator]

hynespa,

Q1) I am not sure what the Fluxgate compass looks like. The one on my boat would be the original one installed with the S3G course computer when the boat was built in 2005. Is there a link to a photo of the 2005 Raymarine fluxgate compass, so that I can correctly identify it when I go searching in the boat for it?
A1) You can find information concerning the autopilot's Fluxgate compass (image shown below) within its installation guide.



Q2) Is there a photo or diagram showing where the gyro is plugged into on a S3G course computer board or step by step instructions on opening the S3G and unplugging the fluxgate?
A2) Unfortunately, product disassembly/repair support is outside of the scope of support which is offered. That said, the S2G/S3G course computer's cover is secured to the chassis by four screws which pass through the front face of the cover ... simply remove these screws to permit the cover to be pulled away from the chassis. The course computer's rate gyro (photo shown below) should be very easy to locate on the processor board and it is the only component having a cable like that shown below.



Q3. I have attached a copy of the Raymarine S3G installation / wiring diagram. In the Fluxgate compass test it says to unplug the transducer and connect the multimeter to combinations of the Red/Green/Yellow/Blue wires. I don't see where the transducer is wired into the S3G - so I want to make sure I'm unplugging the right thing. Could you point out where it is wired into the S3G?
A3. The diagram shown is that of the S3G's power/interface terminals. The terminals labeled Fluxgate are those to which the autopilot's fluxgate compass should be connected.