Changed sears thermostat #387.911120 to a honeywell #rth221b1021/a There are 3 wires from the wall, red to the are, wbite to the W and black to the why. Put them in the same place on the new thermostat as they were on the old. Per instructions from honeywell. Can't get heat. Only cold air. How do I wire the honeywell?

Is there a jumper between Rc and Rh. If not, you need one.