1988 K5 Factory a/c truck (a/c deleted by previous owner)- a buddy helped me out and relpaced my heater core (thank god for mechanic buddies). Only thing is now my vents are all screwed up. Heat pretty much come out the vents and floor only no matter what setting I have it on. My defroster barely works at all which is no bueno. I am guessing it’s my blend door ♂️ Is there a go to you tube video for this or a good schematic? I am too embarrassed to keep asking my buddy to help out even though it may have been something he did or didn’t do when reinstalling the heater core. All suggestions are greatly appreciated thanks.