Parking brake light indicator not turning on

The socket "looks" OK to me. Again, the socket does NOT ground. The circuit path is power----to one side of the socket---through the bulb---out the other socket wire----down to the switch----the switch activates the light when "made." As cruze said, and just like door/ dome lamp switches, the are "made" (grounded) when the plunger is released, as when the door is open.