Vehicle air conditioning systems and methods for operating the same

Vehicle air conditioning systems (2) may include an electrically driven compressor (4, 6) that is electrically connected to an alternator (16) driven by a vehicle engine (18). The compressor may be driven in a first drive mode, in which a normal drive control is performed. The compressor also may be driven in a second drive mode, in which the rotational speed of the compressor is increased, as compared to the normal drive control. The compressor may be driven in the second drive mode at least when vehicle running speed is being reduced.