Ill have to probably recheck this but they flow in through the cowel under the wipers and to the passenger side where you find your recirc door that controls flow of inside or outside air

 

Some of the really cheap heater cores don't have the correct number of tubes and fins to transfer the heat to the air. I'm guessing cardone falls into that category. You'll need to buy a better quality heater core.

 

That’s why I tracked down a OEM copper core... costs a bit more but I don’t want any reason to go back in any time soon.

 

Air pocket in the heater core?

With the actuator off, turn your heat on full blast, and cycle the door back and forth, does the temp change as much as it should?

 

We solved the no-heat issue by simply reversing coolant flow to the heater core. We flushed the system and flipped the hoses. The heat isn't super hot which makes me think there's an air bubble in the core or something, but it works well enough to clear the ice from the windshield and keep me from freezing (but we haven't seen the 40-below temps yet). I was surprised it worked.