1965 Plymouth Valiant oil pressure sensor

I recently installed a new alternator and battery in my 1965 Plymouth Valiant 200 (225 engine). When I started the car after completing the task, the oil prssure light came on and remains lit. I did not touch the sensor when replacing the alternator. There is no wire attached to the sensor and I cannot find any wire discounnected anywhere near the sensor, nor anywhere else under the hood. What gives?

Duplicate post.