Vehicle automatic defrost system and method

A method for reducing condensation of an internal surface of a window of a vehicle comprising:

• detecting, using an external temperature sensor, an ambient air temperature of an environment of the vehicle;
• detecting, using an internal temperature sensor, an inside air temperature of a cabin of the vehicle;
• detecting, using an internal moisture sensor, an inside moisture level of the air inside of the cabin of the vehicle;
• determining, by an electronic control unit (ECU), a difference between the inside air temperature and the ambient air temperature;
• setting, by the ECU, a condensation indicator when the ambient air temperature is less than a first temperature threshold, the difference between the inside air temperature and the ambient air temperature is greater than a second temperature threshold, and the inside moisture level is greater than a moisture threshold;
• determining, by the ECU, a condensation temperature corresponding to a potential temperature of air blown by a heating, ventilation and air conditioning system (HVAC) of the vehicle at which additional condensation will accumulate on the window based on the inside air temperature and the ambient air temperature;
• determining, by the ECU, a desired temperature of air for the HVAC to blow that is warmer than the ambient air temperature and cooler than the condensation temperature based on the inside air temperature and the ambient air temperature;
• and
• controlling, by the ECU, the HVAC to blow air at the desired temperature when the condensation indicator is set.

A system for reducing condensation of an internal surface of a windshield of a vehicle having a longitudinal axis, the system comprising:

• a heating, ventilation and air conditioning system (HVAC) having a vent positioned on or adjacent to a dashboard of the vehicle and a blower configured to blow air through the vent into a cabin of the vehicle at a desired temperature;
• an external temperature sensor configured to detect an ambient air temperature of an environment of the vehicle;
• an internal temperature sensor positioned on or adjacent to the dashboard between a lower edge of the windshield and the vent and configured to detect an inside air temperature of the cabin of the vehicle;
• an internal moisture sensor positioned on or adjacent to the dashboard and configured to detect an inside moisture level of the air inside of the cabin of the vehicle;
• an external moisture sensor configured to detect an ambient moisture level of the air of the environment of the vehicle;
• and
• an electronic control unit (ECU) coupled to the external temperature sensor, the internal temperature sensor, the internal moisture sensor and the HVAC and configured to:
• determine a difference between the inside air temperature and the ambient air temperature,
• set a condensation indicator when the ambient air temperature is less than a first temperature threshold, the difference between the inside air temperature and the ambient air temperature is greater than a second temperature threshold, and at least one of the inside moisture level is greater than a first moisture threshold or the ambient moisture level is greater than a second moisture threshold,
• determine a condensation temperature corresponding to a potential temperature of air from the HVAC at which additional condensation will accumulate on the windshield based on the inside air temperature and the ambient air temperature,
• determine the desired temperature for the air blown by the HVAC that is warmer than the ambient air temperature and cooler than the condensation temperature based on the inside air temperature and the ambient air temperature,
• determine that the air blown by the HVAC should be recycled air when the ambient moisture level is greater than the inside moisture level and fresh air when the ambient moisture level is less than the inside moisture level, and
• control the HVAC to blow air at the desired temperature when the condensation indicator is set.