Did you look real good at the PLUG that attaches to the switch?
Corrosion occurs on the female connectors in the plug, especially the one that goes to the battery.
A lot of times the plastic plug is melted somewhat because of arcing, then heat build up occurs because of poor conductivity.
That leads to removal of the thin anti rust plating, that leads to rust/corosion and,---- well you see the down hill spiral.
If the plug shows any corrosion in the female terminals, replace them on the wire ends.
They are available without replacing the whole harness.
Also they are available as a pigtail with plug.
then one just has to solder/shrink tube the pigtail to existing wire harness.
