95 Peterbuilt 379 electrical problems

Likely you have a frayed wire behind the dash that is shorting out against something.

 

When the flickering and connections get hot..is your volt guage discharging? That would verify a short. Assuming trailer is disconnected mayby start unplugging things. Like tractor tail lights. Just 2 of them or do you have extra lights across the tail of trk? Has a previous owner wired on extra lights. Thats what i usually check first. Jerry rigged wiring, possibility grounding out.

 

In the second photo I can see a butt splice and two different size zipties on the same wire bundle. This is where my money is.