I have a carrier furance the heat works, the ac comp. goes on when I turn the air on but the blower does not come on. There are no fault codes.I can take out the thermostat jump the wires and switch off sw-4 on the control board to turn on what they call emergency heat. Then the blower comes on. I am going to change the thermostat but I think it could be the control board. I would grateful for any help I can get