The light is actually called a key illumination light and comes when the door
is opened but is to go off when the key is inserted into the ignition. I had
the same problem with my '71. The wire feeding it is purple/orange. It goes
to the ignition switch. There is also a purple/orange wire coming from the
driver's side door switch that goes to the ign switch. I pulled the back off
the ign switch and directly connected the P/O wires. Now I have an underdash
light that goes on when the door is open nad off when the door is closed.
Hope this helps.
Mike C CC62976L