First off, this is a 1981 royal night el camino with factory air

Ok so my windows were fogged so I pushed the hot/cold nob over to hot (and felt resestance about half way over) on the bottom slide and went to defrost and after my windows were defrosted I went back over to cold (felt a little harder to push) and a little washer thing with teeth on the inside poped out (I think its the once you push over a ball tiped thing and then you can not pull it off) and put it to max A/C. Then it was only blowing hot air. Now I cant push it over to hot, it only goes about half way but will go all the way to cold but only blow hot air.

Also some times when i turn it form the off postion to max my cheak engine light will come on and my head unit will turn off then back on again.

So tell me what I need to do or tell me what more info you need.

thanks

It sound like the cable controlling your temperature selection has poped off the arm at the heater box and is stuck in the heat position.