On the way to town last summer, my Furuno auto pilot was wandering at least 30 degrees in somewhat calm seas. The heading sensor status light was blinking slowly, as it has done many times in the past without such an error in course. Since the PG500 is not always visible when I am at the helm, I don't know when the output switched to true as I have always used magnetic (or if this had anything to do with my erratic course changes). Thinking that the PG500 heading sensor was failing (this happened in the middle of my fishing season), I ordered another sensor and sent the old one in for repair. The new sensor will also not display magnetic which is the default heading. The old sensor was sent back as their was nothing wrong with it. I am using Nobeltec Navigation software. Shutting the computer down does not change a thing.