An air conditioning system for a vehicle includes a compressor. The vehicle includes
a first drive source and the compressor includes a second drive source. The compressor
is driven by the first drive source or the second drive source, or a combination
thereof, and the second drive source includes an electrical power supply. The air
conditioning system also includes a controller for selecting between the first
drive source and the second drive source, such that when the compressor is active,
the first drive source drives the compressor except when the vehicle is operating
in a predetermined mode, a voltage of the electrical power supply is greater than
or equal to a minimum electrical power supply voltage, and an amount of electric
power consumed by the second drive source is less than a maximum electric power.
For example, the predetermined mode may be an idle-stop mode.