Patent ID: 7392838

Claim:
A method for controlling a vehicle HVAC system, comprising the steps of: calculating a temperature of a window in said vehicle by: measuring a vehicle speed; measuring a temperature of ambient air outside said vehicle; measuring air temperature within the vehicle cabin; if cabin air temperature is below a predetermined temperature, calculating said window glass temperature based upon at least one of said measured vehicle speed and said measured ambient air temperature; if said cabin air temperature is above a predetermined temperature, using said ambient air temperature as said calculated window glass temperature; calculating a dewpoint of air within a cabin of said vehicle; sensing relative humidity of air within said vehicle cabin; determining a fog margin, wherein said fog margin is a difference between said calculated window glass temperature and said calculated dewpoint, said fog margin being related to condensation formation on said vehicle window; wherein said HVAC system is operated in accordance with a predetermined algorithm based upon said fog margin and said sensed relative humidity.