Ford A/C :: No AC And Heat Is On Full All The Time

I just picked up a beautiful 98 Ranger and the only thing I can find wrong with it is a HVAC problem. I bought the truck through the owners brother and they informed me that the AC would work if you "moved something under the dash".

So far, this is what I know:

The temperature out of the vents is full hot, all the time meaning even with the temp control all the way down to cool with the mode selector (Max AC/AC/ Vent/ Off etc.) in any position, all you get is max temp hot air out of the vents. The mode selector does seem to work in as much as it can re- direct the air to the proper outlets when it it operated.

At first I started looking at the AC system itself but now I think it's a control problem. The AC clutch relay, fuse, low pressure switch, clutch field coil, static refrig. pressure and power to the clutch circuit all look OK.

I poked around under the hood looking for vacuum leaks but there was nothing obvious and like I said, the mode selector works, so there's some source of vacuum for them. Also, The hot water valve is actuated when the selector is on the MAX AC or OFF positions as it should be.

Does this sound like a blend door problem? A bad temperature control? I am not well versed in this system and I'm wondering why even if the blend door is stuck or broken (an assumption), the AC compressor will not come on. I have already checked both the selector and the temperature controls to make sure they weren't stripped and spinning on their shafts.