I have a 2001 R/t with the 5.9, 118,00 miles. When the outside temp gets down to 30 I barely have any heat in the cabin. I replaced the thermostat, the engine temp seems to be where it should, and the hoses going to the heater core are hot. (one almost to hot to touch, the other somewhat cooler) It seems like it is only heating outside air and not recirculating and already warmed air from the cabin. Is this correct?