Air conditioning unit for a vehicle and method for operating the same

The unit has a supply channel (11) for air and a blower (12) leading to an evaporator (13). Downstream from the evaporator a heat exchanger (17) is provided. A by-pass channel (14) is provided for by-passing the evaporator. The by-pass channel (14) is adjustable. A flap, adjustable by a control drive, determines the flow of air through the by-pass channel. An independent claim is included for a method for operating the unit.