Exterior light-sensing fixture no longer works
I have the following two-bulb exterior light-sensing fixture on the outside of my house that just stopped working. The bulbs are fine and the breakers are fine, so I'm assuming the light sensor went out. Is that sensor replaceable on such a light fixture? I thought the sensor would just unscrew, but turning it with a pliers just turned the entire mechanism on the inside of the fixture.
Inside of fixture: