House batteries switch not turning DC panel on?

[Lusitano]

As crazy as it sounds yesterday i noticed that my house batteries switch ONLY come on when i turn my start battery switch on

How is this even possible I may ask, since they're separate systems?!?!

 

[Don S/V ILLusion]

It’s not!

“house battery switch comes on” - what does this mean? What “comes on”?

 

[JoeWhite]

I can not follow your description well, if you mean that the house devices work only when the switch is on ALL position, then if you have a fuse for the house batteries it may have blown. This can be tested with a voltmeter at the switch lugs.
More description will help.