When I move the top lever to A/C, power should flow through a light green wire to the diverter door switch, then come to the low fan speed terminal by a gray wire, which activates the low blower speed & simultaneously sends power through a tan wire (which is connected with the gray wire) to the thermal switch, then to the dark green wire to the compressor. What is happening is that there is no power at the light green wire off the control head. Nothing appears melted or out of whack other than that. My guess is that the control head is not allowing power out the light green wire, even though the power supply to the control head is good. Is this indicative of the control head taking a fault? Can these be rebuilt?