Call a professional HVAC service person. Ask them.
Fuel level, heat or air conditioning up, both high and low, high only, floor only. Center vents are for air conditioning output only, no heat. Heat is designed to blow out side and floor vents only. NOT center. Center is only for air conditioning or summer vents.
The air is off.
i would think its on.
If the vents are inside the cab of the truck, this could mean you have blown your heater core.
Air Conditioning
Conditioning of brain/Mind.
If you mean an "orifice tube", then yes.
Air-Con? Do you mean Air Conditioning?
delta t is change in temperature
it means air conditioning.
Define "vent". If you mean to vent crankcase gasses, yes, that's the purpose of a PCV valve. If you mean does the valve cover need vents to facilitate cooling... no. Many rocker covers have vents but it's strictly for decoration.
Do you mean for directing airflow to the different vents?