Stop in for a cup of coffee

You can't use a voltmeter like that. In fact the only meter that can be put in-line is an ammeter
[URL]https://www.web.imperialclub.info/Repair/Lit/Master/067/Page22.htm[/URL]

- unless its an externally shunted ammeter. Then the shunt goes in line and the meter is in parallel.
Like this
View attachment 1716021680
yes, I didn't realize that when I wired it which Is why I was going to Just feed power to the fuse block by tapping into the + side on the voltgauge