The depth gauge on my 2017 R-31 CB did not appear to be working this spring. I checked the transducer and topped up its fluid, which was only slightly below capacity. I turned off all power and then rebooted my electronics. Nothing helped. Then I called our friends at Ranger Tugs, which I should have done in the first place.
They told me that other RT and CW owners were having difficulty getting a readout from their depth gauges after installing the latest Garmin software. The fix after booting up the Garmin system is to open the sonar functions before opening chart functions. This worked like magic for me, although I have to do it each time I boot up the system now.
This seems to be a glitch in one of the Garmin updates published during the winter. Fluid Motion has talked to Garmin about it, but as yet I haven’t seen an acknowledgement by Garmin or any comments about it on Tugnuts. Hopefully this glitch will be fixed soon. But if you are having problems getting a reading from your depth gauge to show on your Chartplotter in chart mode, I suggest you close the chart mode, open the sonar mode until you see a depth reading, and then go back to the chart mode and look for a depth reading. Hopefully, this will solve your problem.