97 Explorer AC/Heater problem

I have a 97 explorer, 5.0 AWD with 143,000 miles. Purchased as second owner and was told from the original owners they always had problems with controls working correctly. Motor speed only worked on low and high which I corrected with new resistor pack. During winter, the heater always blew hot however the temp control would never regulated to a cooler temp. Not an issue as we just shut off heater control. We noticed when the heater was shut off, cold air can be felt on passenger side floor.
The AC did blow cold (switch in AC MAX mode) but towards the end of season temp felt warmer than normal. Thought this was just needing recharged at the time. This last week I had the AC service however the cold air in the vents was only cool at best. Pressure is good and compressor works as it should as told by service people. If you feel above the plenum, it is colder than the air coming out the vents.
I now only have low and high motor speeds again but I can not get cold air out of vents.
Here's is what I have found, looking through the glove box, the vent on the right side of plenum box opens and closes with selector control from heater to AC. The motor on top of plenum DOES work with changing of temperature selction from cool to hot as I popped the motor off the posts and verified it was operating. Is there a vaccum control which is not allowing the system to operate or is it the control unit in the dash? I have not replaced the resistor pack again for the motor and was wondering if that may be causing the problem. Any suggestions would be most appreciated.