Air conditioner units and bulkhead assemblies for air conditioner units are provided. A bulkhead assembly includes a bulkhead which includes a first sidewall, a second sidewall spaced apart from the first sidewall along a lateral direction, and a rear wall extending laterally between the first sidewall and the second sidewall. The rear wall includes an indoor facing surface and an opposing outdoor facing surface. The bulkhead assembly further includes a vent aperture defined in the rear wall, and a vent unit. The vent unit includes a frame, a door, and a hinge rotatably connecting the door to the frame. The frame is positioned on one of the indoor facing surface or the outdoor facing surface and defines a frame aperture generally aligned with the vent aperture. The door is rotatable between an open position and a closed position.