Typically 1/0 is how ON/OFF is stored in the database in the first place. Are you sure you have the scale of your secondary axis set right? Have you tried to chart is by itself?
I have a couple of Switches that I chart and it works just fine, though I’m not using Habmin.
When you said that you can chart many sensor values that implies that you have persistence configured and working. So you just need to add your Switch to persistence just like those Items.
