70 up charging system upgrade question

Dilemma... I still haven't narrowed down the culprit but it's looking like the wires at both of the splices should be replaced. Splice is actually solid. Wires brittle/stiff but no melting. I have another connector that I could "prewire", but not it DOES NOT look to be safe soldering under the dash.
Each splice has 5 wires, so very difficult. Suggestions ?
Here is a pic of splices in a spare harness I have(for visual effect lol)

20181001_211240.jpg