I have a 1998 ranger that is having heater problems. I have heat the problem is I have heat all the time. The Temp control dont work so I replaced it and still the same thing. I replaced the heater control valve in the engine compartment and i have replaced the blower motor resistor all which needed to be done. Still the same problem. I believe the floor vent doors are not opening. I turn on the AC and I get cool air through the vents. Can anyone tell me what I need to do.