Does copper wire go bad?

The initial quality of the copper is a player also. No guessing what mix or quality control was used back then.
Low voltage could be in the park lamp circuit alone or could be found throughout the vehicle. Best place to begin diagnosis ( for me ) is the fuse box. If only the park lamp circuit is weak ? If all hot at switch on circuits are weak ? If both hot at switch on and the hot at all times circuits are all weak ?
Each condition leads to a different place.
Good hunting.