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C80, GPS 125, SPX30, ST8002+ Autopilot head, SeaTalk 1 The autopilot is disconnected from the ST system and operates independently: the C80 shows an "X" through the "Pilot" icon. On recommendation from Derek, a Raymarine Forum moderator and very knowledgeable guy, I disconnected the ST wires (all three) that connected the SPX30 to the ST buss bars. Of course, on the 8002 display, there is only one ST connector back to the SPX30, so with the SPX30 ST connection severed, the two systems are independent.

We are having trouble with the heading information on our C80. Our C80 displays position information as well as COG and SOG information, but often lacks heading information. Today, it's behaving normally, but often, the "No Heading" system alarm sounds every 10-12 seconds, often continuing for hours. Imagine the frustration!

This is the information that we were given by Derek-the-moderator on the Raymarine Forum: "Note that Heading is derived from the SPX30 compass, whereas COG is output from the GPS sensor, the two are not related." Is the mentioned "SPX30 compass" the fluxgate compass? It's the only compass that I know in the Raymarine system. Since the Autopilot system is completely disconnected from the ST system, and therefore the C80, how is the C80 to receive any heading information?

What if a system doesn't have an autopilot? How does the system acquire heading? Surely it's from the GPS. Since, in our system, the Autopilot and the C80 aren't connected via ST, then regardless of how the SPX30 is acquiring the heading data, I don't understand how it can be transmitted to the C80. Except when it's not, the C80 displays heading information with the SPX30 disconnected.

Another interesting point is this. At this moment, the Autopilot is on and steering perfectly: it's still an independent system. We are running on a magnetic heading, so the fluxgate must be functioning, and we've never encountered problems with steering by magnetic heading. The C80 is operating perfectly and seems to have heading information: We are not receiving the "No Heading" system alarm. On the other hand, we cannot use the display choice of, "Heading Up", but only "Course Up", and "North Up". Should this mean that the C80 doesn't have heading information?

There is certainly a ghost in the system but I'm not sure what it is. The system alarm is the problem, of course, since it's persistent and overrides C80 function until the "Acknowledge" button is pressed.

1. Should we send in the C80 for repair? What would be the failure to mention?
2. Should we purchase a new GPS mushroom? Is that the failure point? Can it be repaired? The unit sometimes requires 4-5 minutes for a fix, even when we're in the same location that we de-powered the ST bus that powers the GPS.

Please note that we are manual readers and we read in the C80 manual on page 4-1, "To access full functionality your chart plotter system requires position and heading data from your boat's Global Positioning System." Later, on page 4-3, the manual states, "Note: If neither heading nor COG data is available, the vessel is shown as a solid circle.

We leave French Polynesia in a week and need to have some help in determining what, if any, of our electronics we should take home for repair. Of the Raymarine instruments that we've sent for repair neither has been repaired since they can never reproduce the problem. This has occurred with our non-functioning DSM and our wind transducer. It's not an inexpensive process.