[CA] [CA11] Position fix lost when Autopilot is engaged

[KJB1999]

I have the following electronics on my boat:

Raymarine E120 Classic
4kw Open Array
650 autopilot display head
S2G Course Computer with fluxgate compass
DSM300 Sonar
ST60+ Tri-data
RS 130 GPS

I replaced my original GPS sensor (112 or 120, I can't recall) with a RS130 in 2016 and it is installed using a Seatalk ng to Seatalk converter. The converter is connected to a Seatalk port on the S2G course computer and the converter is not hooked into a power source. After this installation I had no issues during the 2016 season and most of the 2017 season. The issue started at the very end of the 2017 season before the boat went into storage.

The problem is as follows: When running with all systems on (Radar included) if I press "Auto" on the control head for the autopilot the MFD immediately displays an alarm the the position fix has been lost and prompts me to acknowledge. The autopilot returns to standby immediately upon alarm triggering. The position fix is reacquired and the problem repeats itself if I attempt to re-engage the autopilot again.

I tried it with the radar in standby and got the same result except there was a bit of delay before alarm sounded and fix was lost (maybe about 5 seconds or so) versus immediately.

The batteries were all replaced at the beginning of the 2017 season and the output from the alternate on the engine the power the house bank is correct.

I attempted to duplicate the problem at my slip under the following conditions with all systems running:
Shore power connected - no issue
Shore power disconnected - no issue
Generator on and charging system - no issue

Not sure what to test next. Could it be a communication issue where the pilot wants the heading and that causes the MFD to lose it triggering the alarm which then disengages the autopilot? Any ideas would be appreciated. Thank you.

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum KJB1999,

Please click here to view a FAQ addressing how we would recommend that a Raystar 130 GPS Sensor be installed within a system such as yours. I suspect when the autopilot is engaged, the power demands of the powering the drive unit are affecting the power output of the S2G's SeaTalk port. You may want to instead power the SeaTalk bus via the SeaTalk to SeaTalkng Converter as has been specified as a best installation practice. To do so, the SeaTalkng Power Cable supplied with the ST-STng Converter will be connected to a switched 12VDC power circuit and to a spur socket of the ST-STng Converter. Should all spur sockets of the ST-STng Converter be occupied, then please click here to view a FAQ addressing how additional spur sockets may be added to the backbone which has been created from the ST-STng Converter. Next, the red lead of the SeaTalk cable which has been connected to the S2G's SeaTalk port will be disconnected and insulated to prevent shorting. Finally, you will need to verify that if the MFD's SeaTalk/Alarm Cable is connecting the MFD to the SeaTalk bus, that the red lead of this cable is not being used and has been insulated to prevent shorting.

[KJB1999]

Thanks for the info Chuck. I will order those items and then hook the system up as you have described. Thank you.

[Chuck - Raymarine - Moderator]

You're welcome.