A/C blower motor with a mind of it's own

[Earl Filter]

I'm getting around to getting some A/C back in this thing (it's hot in Houston!), and here's what I have:

The blower motor was disconnected at the motor itself when I got the truck. After fiddling with it, I found that when plugged in, the motor will run on low with the truck turned off (and was probably killing the battery, and is why it was unplugged). With the truck on, it blows on low, no matter where the fan selector switch is, except if I move the A/C control to MAX, the fan blows on high, no matter where the fan selector is. If moved to normal A/C, defrost, vent or anything else, the fan blows on low. I bought a blower motor relay for grins, but no change in activity. Is the A/C control head the problem? What do I check next? I bought a new fan switch, but I haven't installed it yet. I figure it will be an exercise in futility, as I don't believe that is where the problem is.

Secondly, when the fan does blow, I get most of the air out of the heater vents, and some from the A/C vents no matter where the contol is set.

How can I go about troubleshooting these issues? Thanks in advance!