Demist control for hvac

A vehicle heating, ventilation, and air cooling (HVAC) system comprising:

• a casing including an evaporator and a heater core;
• a first side window demist outlet defined by the casing;
• a first rib of the casing extending partially across the first side window demist outlet to partially obstruct airflow through the first side window demist outlet;
• a second side window demist outlet defined by the casing;
• a second rib of the casing extending partially across the second side window demist outlet to partially obstruct airflow through the second side window demist outlet;
• a windshield defrost outlet defined by the casing;
• a control door mounted within the casing and movable to open and close each one of the first side window demist outlet, the second side window demist outlet, and the windshield defrost outlet;
• a first wall extending from a first portion of the control door that is opposite to the first side window demist outlet;
• and
• a second wall extending from a second portion of the control door that is opposite to the second side window demist outlet;
• wherein:
• movement of the control door varies position of the first wall relative to the first rib to control airflow through the first side window demist outlet;
• and
• movement of the control door varies position of the second wall relative to the second rib to control airflow through the second side window demist outlet.