I have a 2000 dodge Grand caravan, 3.3 flex engine. The problem is, at an idle there is little or no heat coming from the vents, when the engine rpm is increased either by sitting still and just stepping on the gas or by driving it, the air from the vents warmsup and get hot. The coolant level is good.While driving, the temp gauge comes up to mid point and stays there, so the van is not overheating like a stuck thermostat.
Any ideas?

 

feel both heater lines to the fire wall if one is colder then the other u have a clogged core.

 

heater core or bad water pump .are you sure your system is full??did you look in radiator?