AC Problems on 88 Corvette

[SpeedyKev42]

Wondering if someone can help me out..

I have a 1988 Chevy Corvette that has AC problems. Ok.. When I press the Auto, Bi-Level, or Defroster buttton on the Auto Climate Control unit with the Manual button set to highest speed and the Temperature set to 90 degrees, the Clutch on the air compressor turns on and blows cold air out the vents. However, when I press the Heater or Economy button, the AC clutch does not turn on. I have checked vaccuum hoses and I put a new Programmer in the car. I also hooked up a garden hose and blew out the heater core. And, I just put in a 160 degree thermostat. The blender door does appear to be moving, also. I am wondering if there is some type of relay or sensor that I am overlooking or where else can I look to solve this problem.

Any info would be greatly appreciated at this point in time...