You have been chasing electrical gremlins on that bike for years. All the fuses should have battery voltage regardless of what they power.
Check battery voltage from post to post then from the positive post to the engine and the frame. These readings should be the same. You have a bad connection or a bad ground. Pull out your ignition switch and check the voltage in and out you may have some corrosion inside the switch or at the connectors.
I found some corrosion at the backside of my fuse box and the ignition switch connector before we took the trip out west. Cleaned up the crud and liberally added dielectric grease.. so far so good.
