Why does it feel like my heater is always blowing out the vents?

[WH23G3G]

When I'm driving around already in the 90 degree weather I notice even more heat coming from my a/c vents on my 73 Charger. I put a NOS heater control valve on when I had the motor out, new heater core, and a new heater control cable. I noticed that I'm missing this clip http://www.ebay.com/itm/MOPAR-A-C-B-E-BODY-64-74-CONTROL-ROD-CABLE-CLIP-NEW-ITEM-95004-/350842554239?pt=Vintage_Car_Truck_Parts_Accessories&hash=item51afd8877f&vxp=mtr#ht_978wt_789. I've got the looped end of my control cable over the control lever. According to the 73 Dodge service manual the clip should actually go on the rod control lever and the looped end should be 1/4" away from the lever. So I know I've got the cable adjusted right. I'm wanting to recharge my a/c system but I figured I'd better get this problem fixed first. Is it more of a control cable adjustment issue or would there be a door stuck open on the plenum box? Which one controls the heat coming out of the vents? It's already uncomfortable enough with no a/c but this makes even worse.

[XH29N0G]

I think you know more about this than I do, and mine is a 70 which may be different.  But in case it helps, I will describe what happened with me. 

It had a similar problem and I did two things that made a difference.   The vacuum pot was disconnected so I reconnected it, and (2) the cable to the valve was misadjusted.