Patent ID: 7866169

Claim:
A method for controlling a vehicle HVAC system, comprising the steps of: calculating a window temperature of a vehicle window in a vehicle; sensing a cabin temperature of air within a vehicle cabin of said vehicle; sensing relative humidity of air within said vehicle cabin with a relative humidity sensor, said relative humidity sensor having a predetermined sensor accuracy; calculating a dewpoint based upon said sensed cabin temperature and said sensed relative humidity within said vehicle cabin; determining a fog margin based upon said calculated window temperature and said calculated dewpoint, said fog margin being related to condensation formation on said vehicle window; determining a fog predictability, which is a difference between a calculated relative humidity for condensation at a given temperature and a measured relative humidity for condensation at the given temperature; calculating a humidity margin based upon said sensor accuracy and said fog predictability; and determining a dewpoint margin based upon said calculated dewpoint and said humidity margin; wherein said HVAC system is operated in accordance with a predetermined algorithm based upon said fog margin, said sensed relative humidity, and said dewpoint margin.