Air conditioner units, bulkhead assemblies, and methods for operating air conditioner units are provided. A bulkhead assembly includes a bulkhead which includes a first sidewall, a second sidewall, 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 door movable between an open position and a closed position, wherein in the open position the vent door permits air flow through the vent aperture and in the closed position the vent door inhibits air flow through the vent aperture. The bulkhead assembly further includes a drive assembly connected to the vent door and operable to selectively move the vent door between the open position and the closed position.