Topic: AUX fuse box to power all of our accessories,
Over the years, we've tapped into various places parts of the car harness to power our various accessories and had all the expected trouble from doing so. We finally had enough of that and installed a dedicated AUX fuse box, pictures below.
We are powering the fuse box directly off of the car side of the kill switch, and the ground is connected to a factory ground point.
This fuse box is split into two separate halves, left and right, with separate power inputs. I wired up ours so that the right side powers up off of the kill switch, so that when you close the kill switch, the right side is powered. I used a relay connected to a car accessory line so that the left side powers up only when the ignition key is on.
I put a volt meter gauge connected to the kill switch power on side of the box so that 1) drivers can easily see the battery voltage and I can tell if the battery is dead and 2) if the volt meter is on, you know the kill switch is closed. I connected an LED, mounted next to the volt meter, to the ignition key power side of the fuse box to indicate that the key is on.
This solved all of our electrical power issues, and we are no longer tapping any part of the car harness for power.
This fuse box has LEDs that light up when a fuse is blown.
Here is the fuse box we used: https://www.amazon.com/gp/product/B099ZKFLB1