96 Volvo 850 GLT-Defrost air vent isn't blowing out when I turned selector(control ****) to defrost but always both sides and middle vents blowing not defrost or under dash(floor) vents though I already replaced blower motor and resistor. Speed control and temp(heat/cold) works fine. Changed to different choices but seemed the same, I guess.(it's manual) What will I need to do? Thanks and appreciate!