Go to the Furnace. Try to jumper the R terminal to the W terminal at the furnace and see if the heat and the fan comes on this way?
First check to see if all of the fan speed connections are tight at the control board. On the control board, one fan speed should go to the heat connection and one fan speed should go to the cool connection. Make sure they are hooked up. (Use wiring Diagram located behind furnace panels if neccesary). If everything is in tact you have a bad control board. The control board is not closing the contacts in the fan relay on a call for heat as it is its job to do. You will need to replace the control Board.
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The control board is located inside the furnace panels. You will have to remove the furnace panel doors to access it. If you cannot do this, I would have to advise you to call a tech. out at this point.
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