| CPC B60H 1/3205 (2013.01) [B60H 2001/325 (2013.01); B60H 2001/3257 (2013.01); B60H 2001/327 (2013.01)] | 20 Claims |

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9. A method of operating a vehicle AC system in a vehicle having an engine control unit (ECU), the vehicle AC system including a centrifugal-type refrigerant electric compressor operable to receive refrigerant through an inlet and including a heating unit in heat transfer communication with the inlet, the method comprising:
starting the vehicle in response to an ignition switch operation;
receiving an AC start signal indicating that the AC system is to be activated;
issuing a command to operate the heating unit to cause heat transfer to the refrigerant in the inlet to promote vaporization of liquid refrigerant;
measuring a temperature and pressure at the inlet to the refrigerant electric compressor;
determining, by the ECU, a state of the refrigerant at the inlet based on the measured temperature and pressure;
delaying starting of the refrigerant electric compressor until the refrigerant is determined to be in a vapor state; and
issuing a command to start the refrigerant electric compressor once the refrigerant is determined to be in the vapor state.
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