You're sort of mixing issues. When you enable auto fishing or auto cruising, it will set the gain and clutter automatically for both low and high frequencies. If what you want is to see bottom on the sounder when in deep water, first be sure that you have enabled auto range or set the range manually to a depth greater than the water depth. The sounder is not able to switch automatically between low and high. It is sending out pulse for both low and high all the time it is operating. You can choose which one to display (or display both) but you cannot turn them off individually.
It would not be surprising for the high frequency side of a B275LHW to stop reading bottom past 300-400 feet. However, the low frequency should work to over 1200-1500 feet. If you have your sounder display set to "single frequency", down in the lower left corner of the screen so will see a little bar that says "LF/HF". Just tap "LF" to switch to showing the low frequency output when in deeper water. As I mentioned, there is no automated switching of the frequency displayed as far as I know.
Whether your sounder is operating in CHIRP mode depends upon which "Preset Frequency" setting is in use. You can have three customized choices. If you set one as "Auto CHIRP", your sounder will operate in CHIRP mode.
As for asking questions, I am sure Furuno set up the forum for exactly that purpose so you should certainly take advantage of it. One advantage of the forum is that there are many other folks who have experience operating these systems who may have helpful suggestions to supplement what the Furuno techs provide. If you are trying to troubleshoot a specific problem, you should call Furuno tech support, ideally from your boat. You will find they are extremely helpful and patient and can walk you through steps to identify a problem and solve it. Unlike some other companies, there is usually almost no wait to get through.
