I had a similar problem. I found that the fault was in the wind instrument transducer (a shorted cable?). when I disconnected it from Seatalk, the
chartplotter receives the
GPS signal. Reconnect it and I lose the
GPS fix on the plotter. Try disconnecting other instruments from Seatalk and see if this solves the problem. So now I can either know where the wind is or where I am but not both.