Location: United States, Colorado
While diagnosing an unrelated electrical issue during renovation, I discovered that the junction box containing a fuse and switch, which provides power to my furnace, reads hot with a non contact voltage tester.
It seems to read hot on all of the metal surfaces: the junction box body, plate, and fuse cover.
This seems clearly wrong to me, but the furnace operates normally and I've never had problems with it. Unless there is something unusual about these fuses, it seems to me that a hot wire has come loose or otherwise shorted with the box itself.
Is this a safety issue? Is this box wired correctly? I think yes, but it'd be good to get more input.