a/c heater not working properly

It is a 76 ford LTD with the 351 in it. At first, no air would come out when I turned on the heater or A/C. well I bypasses the fuse box and hooked a switch up from the battery to the resistor and checked the blower motor it worked. After that, I took the switch off. Nothing worked at all of course so I went into the dashboard and took the unit out without unhooking any wires, just looked at it from underneath. I messed around with it and nothing worked still, so I put it back into place and put all the screws in. Now the air is on and when I change the settings it doesn't even go to the setting it is supposed to be, ie. defrost or a/c and so on. Turn on defrost and the air might blow out of the floor. as far as I can tell the cool and heat lever works, and the fan speed lever works. I just got this car so no telling what the other owner did to it before.

I appreciate any help

Chris