Fresh air vent not working on YJ

[cdlongjr]

Got the heater & defrosters working. The fresh air vent isn't operating. I have vacuum at the manifold. The block on the heater controls only has 2 hoses on it. The 3 port, (closest to the steering wheel) is plugged off & I can't find a loose hose under the dash. Where should this port be hooked to?
Also, there are 2 studs on top of the heater controls. Is there supposed to be a cable for the fresh air hooked to the stud closest to the steering wheel? I can't find a 3 rd cable, but the parts list for an 88 shows 3 cables.

 

[cdlongjr]

I was told there was a cable that attached to the left stud on the heater controls & operated the air vent door. I have purchased a new cable but can't figure out where the other end attaches. I have removed the glove box. Where does this cable go?