An air conditioner and a control method for an air conditioner are provided. The air conditioner may include a compressor, a flow switch installed at an outlet side of the compressor, a first guide pipe extending from the flow switch to an outdoor heat exchanger, a second guide pipe extending from the flow switch to an indoor unit, a third guide pipe extending from the outdoor heat exchanger to the indoor unit, a bypass passage extending from the second guide pipe to the third guide pipe to allow at least a portion of the refrigerant in the second guide pipe to be bypassed to the third guide pipe or to allow at least a portion of the refrigerant in the third guide pipe to be bypassed to the second guide pipe, and a bypass valve installed on the bypass passage.