91' Intn'l HVAC Controls gone haywire

[Joneffnah]

I've got a 91 cutlass international ed. with an electronic control display for my HVAC controls. It started going haywire about a year ago. It wouldn't come on, sometimes it would come on for 5 min then get stuck. and so forth. It only blows out heat(really hot!!!) So, I went to a junk yard and got a replacement display. And the same thing still happened. I don't know if it's an electrical problem or not. I had my uncle ,who services HVAC systems, check to see if the compressor is still good and he could even get it to start even if he bypassed the pressre switch on the freon line. I don't even think the compressor is even getting a signal to turn on because of the way the Electronice control display is acting up. I just ordered a Manual Control Module for the HVAC controls, it's in the mail, and I'm waiting to see what that will do. I do most of all the work on my car...
Any suggestions? I'll take any. It gets pretty hot during these summer months.