an automobile air conditioner having a charging device for charging a power source capacitor preliminarily before driving a motor - driven compressor , which comprises a discharge circuit for discharging the electric charge in the capacitor through a power feeding device , and a controller for controlling the discharge by the discharge circuit . further by comprising a cut - off detecting circuit for detecting when the battery is cut off , it is discharged automatically . moreover , the voltage of the battery is converted , and supplied as a power source for the controller .