Defrost..frosting?

[Artemis Entreri]

Ok so first off, my 91 k5 is horrible when it comes to sitting a few hours in the cold, my windshield and driver/pass windows are covered in what I will call frost on the inside, to the point where I have to use paper towels and glass cleaner to be abl to see out of them decently.

Now my defrost has two issues.
first is when its on defrost, I also have heat coming out of the vents infront of the dash, why? Lol

Second is it clears say, the bottom 4-5 inches of the window and the rest fogs up even worse. I've been going back and forth thinking my heater core is going, once in a while I get a quick wiff of antifreeze but then nothing. I was thinking if it Was going, maybe it was blowing moisture out the defrost vents and making it worse? Or something?
Any ideas?

 

[toomany]

I'm guessing that the vacumm valve that controls the direction of the air is broken/leaking in your truck. And that the heater core may have a small leak. I know that a leaking heater core can cause the inside windows to get steamed up.

I'd try searching back a few posts, there have been a couple of topics on the heating system.

 

[odin]

X2 on the heater core leak.....thats whats given ya the fog