I am having a similar issue with my 1994 K1500. The a/c control head is flashing with in the mode area and the temperature. I have tried a new control unit, and new actuators for the blend door actuator and the mode door actuator, yet the problem still exists. I know there is a recirculation actuator in a hard to reach place in the passenger floor area, but I have not tried it yet. I recently heard what seemed like the blower motor making noise, I removed it, found it to be a two wire blower motor when most replacements are a one wire unit, so I tried the blower motor hooked up outside of the heater box and I found no noise. I placed it back in the heater box and the fan speeds are working but I am not getting any air through the front facing vents. I also recently replaced the compressor, condensor, orfice tube, drier, and an a/c line. Any suggestions would be helpful. My next step is to try a new actuator in place of the current recirculation actuator.