Air conditioning system for a motor vehicle

Abstract

An air conditioning system (,) for a passenger compartment of a motor vehicle having a windscreen comprises a first heat exchanger (,) positionable outside the passenger compartment; a second heat exchanger (,) positionable inside the passenger compartment; an expansion device (,) positioned in a first fluid passage (,) between the heat exchangers; an electronically controlled variable stroke compressor (,) for pumping fluid into the second fluid passage and either in a first direction (X) or in a second direction (Y); reverse flow means (,) in the second fluid passage for controlling the direction of the flow of fluid; first sensing means (,) providing a first output signal indicative of the dewpoint temperature of the air leaving the second heat exchanger; second sensing means (,) providing a second output signal indicative of the temperature of the windscreen; and control means (,) electrically connected to the first and second sensing means and to the compressor for receiving the first and second output signals, for determining the dewpoint temperature for the air leaving the second heat exchanger dependent on the first output signal, for determining the windscreen temperature from the second output signal, for comparing the determined dewpoint temperature to the determined windscreen temperature, and for controlling the stroke of the compressor to maintain the dewpoint temperature at or below the windscreen temperature during fluid flow in the second direction. Reduces the risk of internal fogging of the windscreen.