I've got a 93 Z28 LT1 with a heat problem I can't figure out. It has always blown cool air when the heat has been selected. Decided this weekend to replace the heater core as it appeared to be stopped up. I did get it replaced and still have cool air blowing through the vents.
Took the cover back off and the core is getting hot so it is working as it should and the door that moves when switching between cool and hot is moving as it should also as far as i can tell. I can see it moving back and forth when the selector is moved. For some reason when I put the cover back on all I am getting is cool air.

When I move the selector from cool to hot the door moves and the airflow slows down some but there is still no heat through the vents or floorboard. Move it back to cool and the airflow increases. Is there something else that controls the flow of heat? With the cover off it's very warm around the core and the core gets very hot but there is still more cool than hot air passing out with the cover out.

Anyone have any suggestions? I'd really like to have some heat in the car this winter for the first time.

 

Does the defroster work? Did you grab a manual?

 

Yes, defroster works. No, haven't purchased a manual yet. Guess I need to.

 

you can download the factory manual here http://www.mediafire.com/?40mfgeoe4ctti i prefer paper though and 93 is a one book series so no to costly, at least they werent a few years ago. sure sounds like the door is not working right and is not diverting air through the core.