Method for operating a vehicle climate control system

A system for controlling an air conditioner of a vehicle, comprising:

• an air conditioner compressor including a piston and a variable displacement control valve for adjusting a stroke of the piston;
• a clutch mechanically coupled to the air conditioner compressor;
• an electric motor supplying rotational energy to the air conditioner compressor;
• and
• a controller including instructions, executed by the controller, for adjusting the stroke of the piston in response to an evaporator temperature error, the evaporator temperature error being a difference between an expected evaporator temperature and a measured or inferred evaporator temperature, the expected evaporator temperature determined from a desired evaporator temperature received at the controller, and for determining air conditioner compressor torque applied to the electric motor and a torque adjustment to the electric motor in response to the torque of the air conditioner compressor, wherein the stroke adjustment is limited based on available air conditioner compressor torque, wherein the expected evaporator temperature is determined according to an engagement state of an air conditioner compressor clutch and filtering of the desired evaporator temperature.