Check your breakers or use your meeter to see if you have voltage. If so jump out r to g on t-stat. If the fan comes on you have a t-stat problem. If it don't turn fan on you have to look inside the unit and see if you have a fuse link on the circuit board. If you do it may be out or your transformer might be gone out. Check it with a meeter. You should have 24 volts at your t-stat if not check the above areas for the answer.