Burnt wire

There is no ground!
Not in the diagram. Not in the operations.
Take the A/C out of the picture to begin with. Fix the run circuit first. Make sure nothing is grounded. J2 Ignition run - It is NOT fused. It is only 16 gage wires at best so will burn before the fuseable link.

Read through the link I provided.
1972 duster engine harness ECU electronic ignition The circuit codes are actually pretty easy once you understand the format. There's a late 60s MTSC on how to read and use the diagrams if you need.