Turning my authority back on...

[Rawze]

(07-08-2019 )Waterloo Wrote:  ...
I used the cab back wall, ground off the paint
...

Most prostars do not have a solid, direct-route ground connection to the cab and many of its other metal surfaces. In fact, the only real bonding point of the cab is right up at the very front, next to the plugs on the firewall, and it is not a very big set of wires.

If you want to use the metal surfaces of the cab, its sheet metal, or framework for any kind of current-draw, so that you can run things, then you need to add a heavy-gauge jumper directly between the truck batteries and the bottom of the cab, out near the batteries. Just make sure it has some flex in it so when the cab goes up and down, it does not weaken over time.