Truck shuts down when I turn on my lights switch

If it’s not the problem, it’s surely a good place to start.

 

Got access to a multimeter? Verify all those wires with red heat shrink on the ends are connected. If they are just get a bolt and nut and bolt them all together and wrap liberally with black tape.
Then this weekend take @blairandgretchen advice.

 

Didn’t think of that.

It’s just a connection block - right?

 

Looks like it to me.

Edit: Of course I never claimed to be a mechanic, but I am fairly good with electrical so...
If I randomly seen that I would think nothing of it being a connection block, but vehicles do their own things.