HVAC MODULE WITH ANTI-BACKFLOW CONTROL AND METHOD OF OPERATION

HVAC module (200) has an air inlet (201), an evaporator (204) downstream of the blower and a heater (206) downstream of the evaporator (204), and a rear mixing zone (216) downstream of the evaporator (204) and the heater (206), wherein a control valve (290) prevents cold air from flowing back towards the hot air by regulating the pressure of the cold air. A method is devised to control anti-backflow control valve (290) of such an HVAC module (200) by the steps of reading pressure and temperatures at various points in the HVAC module (200); setting air flow and temperature discharge targets; calculating the resistance of the control valve (290) and a blend valve (224b); determining corresponding control valve (290) and blend valve (224b) positions; and moving the control valve (290) and blend valve (224b) to those corresponding positions.