Problem: No A/C or Heater in my 1989 Corvette. Car has the GM climate control with digital sets. Blower works fine and hoses heat up as they should. Compressor engaged intermittently with the A/C and defrost but no longer will engage. Thermostat is fine. Two mechanics (not Chevy or Corv specialists) have cried uncle. Their best guess is the climate controller, and take it to the dealer. Before taking that assuredly costly and not always satisfactory step wonder if you have an idea about what may be wrong. Tks