A little help please.

[kevinr1970]

I searched this forum, but couldn't find the answer I was looking for. If someone knows of a thread that addresses this question please post a link or give me an idea of where to look.

So, in my '82 K5 2wd I get heat out of the vent in abundance. The problem is I can't get it to change over from the "vent" to the defroster or the heater. I thought I had read something here about what controls the ducts for the defrost/vent/heat (vaccum)? When I operate the switch on the dash, the cable moves the lever behind the dash, but I don't hear any thing change?
There is a "ball" shaped thing behind the A/C box that had a vaccum line that went nowhere and was obviously burnt from touching something real hot (like the headers?). On the engine I swapped into the truck there was a line I could not account for coming off the side of the carb. I thought it went to the ball thing on the other truck so I plugged it in there but nothing changed.
Does this thing have something to do with my heat/defrost/vent controls? And if so, where would the other end of it go?