Recomendations and possible Causes

[Gradius]

Greetings, I know i have a real problem here but would like others to comment on what could cause this to happen.

I have attic wiring that has heated and split. It is old 2/14 wire that is plastic exterior with all wire wrapped in paper. The wire seems to have heated enough to blacken the pink blow in insulation right next to it.
We are going to have to replace all this wire in the attic.

I am gonig to follow the wires that exibit this problem and replace them all and replace the Boxes that are not air sealed IC rated as i go.

Some wires do not show this problem thank goodness. It is the lines that lead into the washroom that do. I have not made my way across the attic yet to dig them all out.

Is there anything else that i should be looking for while correcting this?

Thank you.

 

[telectrix]

if in doubt replace the lot, giving due consideration to cable load/s and hence selecting correct size of cable. not sure of american regulations, but here we'd make sure that the cables contained ground wire/s.

 

[M-Ty]

Might it be similar to polystyrene leaching the plasticiser from the PVC sheath of the cable but not going in far enough to actually destroy it or reach the cores, rather than overheating?