Humidity control method for a variable capacity vehicle climate control system

An improved vehicle climate control system (10) in which the passenger compartment temperature and humidity are controlled without requiring a humidity sensor. The control is based on the recognition that the air temperature (EOAT) at the evaporator outlet represents the dew point of the air supplied to the passenger compartment, and may be specified based on the desired passenger compartment air temperature (SET TEMP) to achieve a desired relative humidity in the vehicle once the desired passenger compartment temperature has been achieved. In a first mechanization, the desired relative humidity is predetermined, and the corresponding values of evaporator outlet air temperature are determined as a function of the desired passenger compartment temperature. In a second mechanization, the operator of the vehicle is permitted to select a desired relative humidity (HUMdes), and the corresponding values of evaporator outlet air temperature are determined as a function of the desired passenger compartment temperature and the selected humidity level.