Abstract: The invention concerns a method using a system (10) for heating or cooling air in a motor vehicle passenger compartment provided with a windscreen, by input into the passenger compartment air which has passed through an exchanger (12) comprised in a refrigerant loop. The invention is characterized in that it comprises steps which consist in measuring the temperature of the air leaving the exchanger (12), measuring the humidity of the air leaving the exchanger (12), determining the dew point of the air leaving the exchanger (12) based on said temperature and humidity, determining the windscreen temperature, comparing the dew point with the windscreen temperature and stopping the heating of air in the passenger compartment when the dew point is higher than the windscreen temperature.

Abstract: The invention concerns a method using a system (10) for heating or cooling air in a motor vehicle passenger compartment provided with a windscreen, by input into the passenger compartment air which has passed through an exchanger (12) comprised in a refrigerant loop. The invention is characterized in that it comprises steps which consist in measuring the temperature of the air leaving the exchanger (12), measuring the humidity of the air leaving the exchanger (12), determining the dew point of the air leaving the exchanger (12) based on said temperature and humidity, determining the windscreen temperature, comparing the dew point with the windscreen temperature and stopping the heating of air in the passenger compartment when the dew point is higher than the windscreen temperature.

Abstract: An air conditioning system (10) for a passenger compartment of a motor vehicle comprises a first heat exchanger (14) positionable outside the passenger compartment; a second heat exchanger (18) positionable inside the passenger compartment; an expansion device (16) positioned in a first fluid passage (22) between the heat exchangers; an electronically controlled variable stroke compressor (12) for pumping fluid into the second fluid passage and either in a first direction (X) or in a second direction (Y); reverse flow means (32) in the second fluid passage for controlling the direction of the flow of fluid; first sensing means (36) providing a first output signal indicative of the actual temperature of the air leaving the second heat exchanger; second sensing means (40) providing a second output signal indicative of the humidity of the air leaving the second heat exchanger; third sensing means (46) providing a third output signal indicative of the temperature of the air in the passenger compartment; and contr